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Key value for chemical safety assessment

Effects on fertility

Description of key information

In a Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test, conducted according to OECD Test Guideline 422 and in compliance with GLP, the NOAEL for parental toxicity was concluded to be 25 mg/kg bw/day and a NOAEL for developmental effects was concluded to be 75 mg/kg bw/day. For parents, the NOAEL was based on decreased fertility at 250 mg/kg/day as well as macroscopic and microscopic changes with corresponding decreases in weights for the male reproductive organs at 250 mg/kg/day (WIL Research Laboratories, 2005).

Link to relevant study records
Reference
Endpoint:
one-generation reproductive toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2005
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Crj: CD(SD)
Sex:
male/female
Details on test animals or test system and environmental conditions:
ANIMAL RECEIPT AND ACCLIMATION
One hundred female and fifty male, sexually mature Crl:CD®(SD)IGS BR rats were received from Charles River Laboratories, Inc., Raleigh, North Carolina on April 27, 2004. The animals were 57 days old upon receipt. Each animal was examined by a qualified technician on the day of receipt, sexed and weighed 1 day after receipt. Each rat was uniquely identified by a Monel® metal eartag displaying the animal number and housed for 15 days for acclimation purposes. During the acclimation period, the rats were observed twice daily for general changes in appearance or behavior. The animals were allowed a pretreatment week during which they did not receive the test article but their clinical conditions and body weight and food consumption data were recorded during that time.

ANIMAL HOUSING
Upon arrival and until pairing, all animals were individually housed in clean, stainless steel wire-mesh cages suspended above cage-board. The cage-board was changed three times per week. The reproductive phase females were paired for mating in the home cage of the toxicity phase male of the same treatment group. Following positive evidence of mating, the reproductive phase females were individually housed in plastic maternity cages with nesting material, ground corncob bedding (Bed-O'Cobs®; The Andersons, Industrial Products Division, Maumee, Ohio). The nesting material is periodically analyzed by the manufacturer for contaminants. No contaminants were present in the bedding at concentrations sufficient to interfere with the outcome of the study. The results of these analyses are maintained at WIL Research Laboratories, LLC. The females were housed in these cages through lactation day 4, the scheduled day of necropsy. Females for which there was no evidence of mating were placed in plastic maternity cages with nesting material upon completion of a 14-day mating period. Females that did not deliver were necropsied on post-mating day 25. Animals were housed in accordance with the Guide for the Care and Use of Laboratory Animals (National Research Council, 1996). The animal facilities at WIL Research Laboratories, LLC are accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC International).

DIET, DRINKING WATER AND MAINTENANCE
The basal diet used in this study, PMI Nutrition International, LLC, Certified Rodent LabDiet® 5002, is a certified feed with appropriate analyses performed by the manufacturer and provided to WIL Research Laboratories, LLC. Feeders were changed and sanitized once per week. Municipal water supplying the facility is sampled for contaminants according to standard operating procedures. The results of the diet and water analyses are maintained at WIL Research Laboratories, LLC. No contaminants were present in animal feed or water at concentrations sufficient to interfere with the objectives of this study. The basal diet and reverse osmosis-purified (on-site) drinking water, delivered by an automatic watering system were provided ad libitum throughout the acclimation period and during the study.

ENVIRONMENTAL CONDITIONS
All rats were housed throughout the acclimation period and during the study in an environmentally controlled room. The room temperature and humidity controls were set to maintain daily averages of 71 ± 5°F (22 ± 3°C) and 50 ± 20% relative humidity. Room temperature and relative humidity were monitored using the Metasys DDC Electronic Environmental control system and were recorded approximately hourly. These data are summarized in Appendix B. Actual mean daily temperature ranged from 69.9°F to 75.2°F (21.1°C to 24.0°C) and mean daily relative humidity ranged from 39.0% to 48.9% during the study. Light timers were calibrated to provide a 12-hour light (6 a.m. to 6 p.m.) / 12-hour dark photoperiod. The 12-hour light / 12-hour dark photoperiod was interrupted as necessary to allow for the performance of protocol-specified activities. Air handling units were set to provide approximately 10 fresh air changes per hour.
Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
The vehicle and test article formulations were administered orally by gavage, via 15-gauge, polypropylene-shafted silicone-bulb-shaped-tipped dosing cannulae (Instech Solomon, Plymouth Meeting, Pennsylvania) once daily.
Details on mating procedure:
Following a minimum of 14 days of treatment, one female assigned to the reproductive toxicity phase was cohabited with one male rat of the same treatment group. The selected males and females were approximately 12 weeks old when paired for mating. Animals were selected for pairing based on ear tag number; the male with the lowest animal number was paired with the female in the same dose group with the lowest animal number, continuing in increasing numerical eartag order until all animals were paired. A breeding record containing the male and female identification numbers and start of cohabitation was prepared. Positive evidence of mating was confirmed by the presence of a vaginal copulatory plug or the presence of sperm in a vaginal lavage. Each mating pair was examined daily. The day on which evidence of mating was identified was termed gestation day 0 and the animals were separated. A maximum of 14 days was allowed for mating. Females that had not shown evidence of mating in 14 days were placed in plastic maternity cages containing nesting material.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Prior to the initiation of dosing (May 5, 2004), representative control and test article formulations were prepared. Duplicate samples (1 mL each) for homogeneity determination were collected from the top, middle and bottom strata of the 25, 75 and 250 mg/kg bw/day dosing formulations and from the middle stratum of the control group preparation. The aliquots dispensed for homogeneity were representative of the size of aliquots dispensed for daily dosing procedures and included resuspension analysis over the longest period of aliquot storage. Samples from the control formulation and samples from the top and bottom strata were withdrawn from the aliquots after 6 and 12 days of refrigerated storage to confirm resuspension homogeneity and stability of the test article in the formulations. Fourteen-day refrigerated stability was assessed by comparison of the test article concentrations from samples collected from the middle stratum of each formulation on the day of preparation and following 14 days of storage. Duplicate samples (1 mL each) were collected from the middle stratum of each formulation, including the control group, for study weeks 0, 1, 2, 4 and 6 for confirmation of concentration. Characterization of the test article structure was performed by gas chromatography (GC) with mass selective detection (MSD). The determination of vinyl-tris(2-methoxyethoxy)silane in dried/deacidified corn oil formulations was performed by gas chromatography (GC) with mass selective detection (MSD).
Duration of treatment / exposure:
Exposure period: 28 days
Four groups of male and female Crl:CD(SD)IGS BR rats (10/sex/group) were administered the test article, vinyl-tris(2-methoxyethoxy)silane, in the vehicle, dehydrated, deacidified corn oil, daily by oral gavage for 28 days; the males were treated 14 days prior to mating and continuing throughout mating. Additionally, four groups of female rats (10 per group) were mated with the treated males and were also administered the test article by oral gavage daily for a minimum of 14 days prior to mating, throughout mating and gestation and continuing through lactation day 3.
Frequency of treatment:
daily
Details on study schedule:
Premating exposure period (males): 14 days
Premating exposure period (females): 14 days
Duration of test: 14 days prior to mating, throughout mating and gestation and continuing through lactation day 3
Dose / conc.:
25 mg/kg bw/day (nominal)
Dose / conc.:
75 mg/kg bw/day (nominal)
Dose / conc.:
250 mg/kg bw/day (nominal)
No. of animals per sex per dose:
10/sex/group
Control animals:
yes, concurrent vehicle
Details on study design:
Four groups of male and female Crl:CD (SD)IGS BR rats (10/sex/group) were administered the test article, vinyl-tris(2-methoxyethoxy)silane, in the vehicle, dehydrated, deacidified corn oil, daily by oral gavage for 28 days; the males were treated 14 days prior to mating and continuing throughout mating. Additionally, four groups of female rats (10 per group) were mated with the treated males and were also administered the test article by oral gavage daily for a minimum of 14 days prior to mating, throughout mating and gestation and continuing through lactation day 3. Dose levels were 0, 25, 75 and 250 mg/kg/day for the mated males, unmated females (toxicity phase) and mated females (reproductive phase). 
Parental animals: Observations and examinations:
All animals were observed twice daily for appearance and behavior. Clinical observations, body weights and food consumption were recorded at appropriate intervals. In addition, detailed clinical observations (functional observational battery [FOB] conducted out of the home cage) and locomotor activity were evaluated for all adult male and toxicity phase females once prior to the start of test article administration (baseline evaluations) and again during the last week of the test article administration.
Litter observations:
All reproductive phase females were allowed to deliver and rear their offspring to lactation day 4; surviving dams and pups were euthanized and examined on lactation day 4. On the day parturition was initiated (PND 0), the pups were sexed and examined for gross malformations, and the numbers of still born and live pups were recorded. Individual gestation length was calculated using the date delivery started. Abnormal behavior of the offspring was recorded. The dam and litter remained together until PND 4.
Postmortem examinations (parental animals):
 Clinical pathology assessments (hematology and serum chemistry) and macroscopic and microscopic examinations (including organ weights) were also performed on the appropriate groups of adult males and toxicity phase females.For females that delivered or had macroscopic evidence of implantation, the numbers of former implantation sites and corpora lutea were recorded. Recognizable fetuses for the females euthanized in extremis were examined externally and preserved in 10% neutral-buffered formalin. For females that failed to deliver, a pregnancy status was determined. Uteri with no macroscopic evidence of implantation were opened and subsequently placed in a 10% ammonium sulfide solution for detection of early implantation loss.
Postmortem examinations (offspring):
Intact offspring dying from PND 0 to 4 were necropsied. Cannibalized pups were discarded without necropsy. Tissues were preserved in 10% neutral-buffered formalin for possible future histopathologic examination only as deemed necessary by gross findings. The carcass of each pup was then discarded.
Statistics:
Mating, fertility, copulation and conception indices were analyzed using the Chi-square test with Yates’ correction factor (Hollander and Wolfe, 1999). Mean litter proportions (percent per litter) of pup viability and percent males at birth were subjected to the Kruskal-Wallis nonparametric ANOVA test to determine intergroup differences (Kruskal and Wallis, 1952). If the ANOVA revealed statistically significant (p<0.05) intergroup variance, the Mann-Whitney U-test (Kruskal and Wallis, 1952) was used to compare the test article-treated groups to the control group.
Reproductive indices:
Male (Female) Mating Index (%)
Male Fertility Index (%)
Male Copulation Index (%)
Female Fertility Index (%)
Female Conception Index (%)
Offspring viability indices:
On the day parturition was initiated (PND 0), the pups were sexed and examined for gross malformations, and the numbers of still born and live pups were recorded.
Clinical signs:
no effects observed
Description (incidence and severity):
There were no test substance-related clinical findings in the reproductive phase females.
Dermal irritation (if dermal study):
not examined
Mortality:
mortality observed, non-treatment-related
Description (incidence):
In the reproductive phase, one female in the 75 mg/kg bw/day group was euthanized in extremis on gestation day 22. The cause of moribundity for this female was considered to be dystocia. In addition, one female in the 250 mg/kg bw/day group had total litter loss on lactation day 0 and one female in the 75 mg/kg bw/day group had total litter loss on lactation day 2. All other reproductive phase females survived to the scheduled necropsy. There were no test article-related clinical findings in the reproductive phase females.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
There were no test substance-related effects on mean body weights and body weight gains during the pre-mating period in the reproductive phase females. However, mean gestation body weight gains were reduced in the 250 mg/kg bw/day group females throughout gestation; mean body weight on gestation day 20 was 22.1% lower than the control group value. Reductions in mean body weight and body weight gain late in gestation were attributed to the increased number (five of nine) of entirely resorbed litters in the 250 mg/kg bw/day group. Evaluation of lactation body weight in the 250 mg/kg/day group was precluded by reduced fertility, embryonic death and total litter loss. No test article-related effects on mean gestation or lactation body weight gains was observed in the 25 and 75 mg/kg/day group reproductive phase females.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
There were no test article-related effects on mean food consumption during the pre-mating period in the reproductive phase in the 250 mg/kg bw/day group females.
Throughout gestation, a statistically significant reduction in the mean maternal food consumption was observed in the 250 mg/kg bw/day group. This was considered to depend on the poor reproductive performance and therefore, secondary to test substance.
No test article-related effects on mean gestation or lactation body weight gains were observed in the 25 and 75 mg/kg bw/day female group.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
Test substance-related decreases in the red and white blood cell parameters were observed in the 250 mg/kg bw/day male and female group. In these groups, the decreases in red blood cell indices were observed with mean red blood cell count, hemoglobin, hematocrit mean corpuscular hemoglobin concentration and percentage and absolute reticulocyte count. Additionally, there was a statistically significant decrease in the mean platelet counts and decreases in the mean white blood cell count, although not statistically significant, which were considered as test substance related. Furthermore, test substance related, statistically significant variations in white blood cell differential evaluation included decreases in basophils and eosinphils and an increase in monocytes.

In the 250 mg/kg bw/day male and female groups, changes in the granulocyte and erythrocoid series were observed. The myeloid:erythoid (M/E) ratio was decreased in males and females. Additionally, the percentages of myelocyte neutrophil, metamylocute neutrophil, band neutrophil, segmented neutrophil, eosinophil and total granulocytes were decreased in the 250 mg/kg bw/day male and groups. The relative percentages of rubriblasts, prorubriblasts, rubicytes, erythroid mitotic figures and total erythrocytes were increased in theses males and females. The increased percent erythrocytes in the bone marrow consisted of an increase in the erythroid proliferation pool (immature erythrocytes). This correlated with the decreases observed in red blood cell count, hemoglobin and hematocrit. No evidence of a reticulocytosis was evidenced supportive of a non-regenerative response at the peripheral level. However, review of bone marrow histopathology showed minimal to mild hypoplasia in some of the animals in the 250 mg/kg bw/day. Therefore, the relevance or mechanism for the cytologic changes cannot be determined.

Statistically significant decreases in mean hematocrit and hemoglobin were observed in the 250 mg/kg bw/day male group and in hemoglobin in the 75 mg/kg bw/day male group. Furthermore, decreased mean activated partial thromboplastin time was observed as well as an increase in the percent prorubricytes in the bone marrow in the 75 mg/kg bw/day male group. However, there was no dose response and/or only small variations from the control values occurred and consequently, these changes were considered as not test substance related.

Statistically significant increased prothrombin time in the 250 mg/kg bw/day female group and increased mean corpuscular volume the 25 and 75 mg/kg bw/day female groups were observed. However, these changes were not considered as test substance-related.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
A statistically significant decreased mean albumin, total protein and globulin levels and increased mean albumin/globulin ratio was noted in the 250 mg/kg bw/day male and female groups. These changes were considered as test substance related effects. Furthermore, statistically significant increased mean bilirubin level in the 250 mg/kg bw/day and mean chloride levels in the 25 and 75 mg/kg bw/day male groups occurred. Decreased mean blood urea nitrogen levels were observed in the 25 and 75 mg/kg bw/day female groups. These changes were not considered as adverse effects since there was not a dose response and similar trend in the opposite sex or small variations compared to control occurred.
Urinalysis findings:
not examined
Behaviour (functional findings):
no effects observed
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
In the 250 mg/kg bw/day dose male group, minimal to mild hypocellularity of the sternal bone marrow was observed in 5 of 10 males and in 2 of 10 females; aggregates of mature granulocytes were absent from histologic sections of the affected marrow; in the thymus, minimal to moderate lymphoid depletion was observed in 7 of 10 males and 3 of 10 females which correlated to reduced thymus gland weights; mild lymphoid depletion of the mandibular (3 of 9 males and 5 of 10 females) and/or mesenteric lymph nodes (5 of 10 males and 3 of 10 females). These changes were considered as test substance-related. In the 250 mg/kg bw/day female group, 2 animals had lymphoid depletion in the mesenteric lymph node although this was not considered as test substance related since the thymus and mandibular lymph nodes were unaffected.

In the 250 mg/kg bw/day dose female group, minimal to mild hypocellularity of the sternal bone marrow was observed in 2 of 10 animals. Aggregates of mature granulocytes were absent from histologic sections of the affected marrow. Hypocellularity of the bone marrow was considered a consistent finding with the hematology alterations.

In the spleen, capsular fibrosis was observed in 4 of 10 males and 3 of 10 females in the 250 mg/kg bw/day male group. This change was noted as adhesions to various abdominal structures or as white areas on the spleen. In contrast to the changes in hematopoietic cell numbers in the bone marrow and lymphoid depletion in the 250 mg/kg bw/day group in various tissues, red and white pulp components of the spleen appeared within normal limits. 2 males in the 75 mg/kg bw/day group had adhesions observed macroscopically although neither had capsular fibrosis.

In the testes, moderate to severe and bilateral seminiferous tubule degeneration was observed in 10 of 10 males in the 250 mg/kg bw/day male group. This correlated with decreased testicular organ weights, macroscopic findings (small and/or soft testes) and reduced fertility. Degeneration was characterised by a marked reduction or absence of spermatogeni epithelium. Minimal seminiferous tubule degeneration was observed in one control male and this was considered as incidental or background changes unrelated to treatment. Similarly, mild degeneration was observed in one male in the 25 mg/kg bw/day group and was associated with the absence of one epididymis which was considered as a spontaneous condition unrelated to the test substance.
Secondary to the extensive loss of spermatogenesis in the 250 mg/kg bw/day male group, all animals had mild to moderate hypospermia in the epididymides and 9 of 10 animals had luminal cellular debris. Hypospermia correlated to the decreased epididymal weights and macroscopic findings why it was considered as treatment related.

In the prostate, decreased section and/or atrophy was observed in 4 of 10; 6 of 10; 6 of 10 and 10 of 10 animals in the 0, 25, 75 and 250 mg/kg bw/day respectively. However, the number of animals within these groups having both decreased secretion and atrophy was 0 of 10; 1 of 10; 1 of 10 and 6 of 10 animals. The combination of these changes correlated with the decreased prostate weights in the 250 mg/kg bw/day group. Decreased secretion was characterised by extensive regions of acini devoid of eosinophilic secretory material (in the absence of free secretory material suggestive of post mortem/artefactual leakage) or small acini due to reduced amounts of secretory material often with a convoluted epithelial surface composed of enlarged cells. Atrophy was characterised by a similar reduction in secretory material, however, also by a marked thinning of the epithelium. Decreased secretion and atrophy were both considered as test substance related in the 250 mg/kg bw/day. it was unclear which change, atrophy or decreased secretion that was the largest contributor to the decreased prostate weights observed in the 250 mg/kg bw/day group. A histological correlation for the significantly reduced prostate weights in the 75 mg/kg bw/day group was unclear. However, the slightly increased incidence of atrophy in this group compared to the control group and finding mildly severe (compared to minimal) atrophy only in the 75 and 250 mg/kg bw/day groups, suggesting that prostatic atrophy may be the greater influence on the prostate weight decreased and may a test substance related change in the 75 mg/kg bw/day. No other test substance-related findings were observed.
Histopathological findings: neoplastic:
not examined
Other effects:
not examined
Reproductive function: oestrous cycle:
not examined
Reproductive function: sperm measures:
not examined
Reproductive performance:
effects observed, treatment-related
Description (incidence and severity):
One female in the 250 mg/kg bw/day group had total litter loss on lactation day 0 and one female in the 75 mg/kg bw/day group had total litter loss on lactation day 2. All other reproductive phase females survived to the scheduled necropsy. Male and female fertility indices were 60.0% in the 250 mg/kg bw/day group compared to 90.0% in the control group. The mean number of days between pairing and coitus was increased in the 250 mg/kg bw/day group. Mean gestation length was increased in the 75 mg/kg bw/day group and in the single female in the 250 mg/kg bw/day group that delivered.
Key result
Dose descriptor:
NOAEL
Effect level:
25 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
gross pathology
histopathology: non-neoplastic
reproductive performance
Critical effects observed:
yes
Lowest effective dose / conc.:
25 mg/kg bw/day (nominal)
System:
other: male and female reproductive system
Organ:
other: Test article-related effects on reproductive performance were observed in males and females.
Treatment related:
yes
Dose response relationship:
yes
Relevant for humans:
not specified
Clinical signs:
no effects observed
Description (incidence and severity):
The general physical condition of pups in the 25 and 75 mg/kg bw/day groups were unaffected by maternal test article administration.
Dermal irritation (if dermal study):
not examined
Mortality / viability:
mortality observed, non-treatment-related
Description (incidence and severity):
Of the nine reproductive phase females in the 250 mg/kg bw/day group with evidence of mating, three were nongravid and five had entirely resorbed litters. Only one female in this group delivered, but all pups were found dead on postnatal day (PND) 0. Postnatal survival in the 75 mg/kg/day group was reduced throughout the lactation period (days 1-4), primarily due to one female with total litter loss on lactation day 2; the differences from the control group were not statistically significant but were considered test article-related. A slight increase was observed in the number of pups found dead or missing and presumed cannibalized in the 75 mg/kg bw/day group. No internal findings in the pups found dead or at the scheduled necropsy were attributed to maternal test article administration.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
Pup body weights could not be evaluated since the pups were found dead on postnatal day 0. The mean body weights and body weight gains of pups in the 25 and 75 mg/kg bw/day groups were unaffected by maternal test article administration.
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Sexual maturation:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
no effects observed
Histopathological findings:
not examined
Other effects:
effects observed, treatment-related
Description (incidence and severity):
Of the nine reproductive phase females in the 250 mg/kg/day group with evidence of mating, three were nongravid and five had entirely resorbed litters. Only one female in this group delivered, but all pups were found dead on postnatal day (PND) 0, precluding evaluation of pup body weights. In the 75 mg/kg bw/day group, the mean numbers of implantation sites, pups born and live litter size on PND 0 were reduced while the number of unaccounted for implantation sites was increased. These effects were considered test article-related; however, only the live litter size on PND 0 was statistically significantly different (p<0.01) from the control group.
Behaviour (functional findings):
not examined
Developmental immunotoxicity:
not examined
Of the nine reproductive phase females in the 250 mg/kg/day group with evidence of mating, three were nongravid and five had entirely resorbed litters. Only one female in this group delivered, but all pups were found dead on postnatal day (PND) 0, precluding evaluation of pup body weights. In the 75 mg/kg/day group, the mean numbers of implantation sites, pups born and live litter size on PND 0 were reduced while the number of unaccounted for implantation sites was increased. These effects were considered test article-related; however, only the live litter size on PND 0 was statistically significantly different (p<0.01) from the control group. Postnatal survival in the 75 mg/kg/day group was reduced throughout the lactation period (days 1-4), primarily due to one female with total litter loss on lactation day 2; the differences from the control group were not statistically significant but were considered test article-related. A slight increase was observed in the number of pups found dead or missing and presumed cannibalized in the 75 mg/kg/day group. The general physical condition and mean body weights and body weight gains of pups in the 25 and 75 mg/kg/day groups were unaffected by maternal test article administration. No internal findings in the pups found dead or at the scheduled necropsy were attributed to maternal test article administration.
Key result
Dose descriptor:
NOAEL
Generation:
F1
Effect level:
75 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Based on reduced post-natal survival during lactation.
Critical effects observed:
no
Reproductive effects observed:
yes
Lowest effective dose / conc.:
25 mg/kg bw/day
Treatment related:
yes
Relation to other toxic effects:
reproductive effects in the absence of other toxic effects
Dose response relationship:
yes
Relevant for humans:
not specified
Conclusions:
In an one-generation reproductive toxicity study, conducted according to OECD test guideline 422 and in compliance with GLP, a NOAEL for males and females was concluded to be 25 mg/kg bw/day. This was based on decreased fertility at 250 mg/kg bw/day, macroscopic and microscopic changes with corresponding decreases in weights for the male reproductive organs at 250 mg/kg bw/day and the reduced mean litter size in the 75 mg/kg bw/day group.
Effect on fertility: via oral route
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
25 mg/kg bw/day
Study duration:
subacute
Species:
rat
Effect on fertility: via inhalation route
Endpoint conclusion:
no study available
Effect on fertility: via dermal route
Endpoint conclusion:
no study available
Additional information

Although the only reproductive toxicity study available for the registered substance is a Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test (OECD Test Guideline 422) classifiable signs of adverse effects on reproductive parameters were observed for male and female rats.

In the key Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test, conducted according to OECD Test Guideline 422 and in compliance with GLP, the NOAEL for parental reproductive toxicity was concluded to be 25 mg/kg bw/day based on reduced mean gestation body weight gains and food consumption in the 250 mg/kg bw/day group female rats (GD 20 was 22.1% lower than the control group). Effects on body weight late in gestation were attributed to the increased number (five of nine) of entirely resorbed litters in the 250 mg/kg bw/day group. Evaluation of lactation body weight and food consumption in the 250 mg/kg bw/day group was precluded by reduced fertility, embryonic death and total litter loss. There were no such effects in the 25 and 75 mg/kg bw/day group reproductive phase females. In the reproductive phase, one female in the 75 mg/kg bw/day group was euthanized in extremis on gestation day 22. The cause of moribundity for this female was considered to be dystocia. In addition, one female in the 250 mg/kg bw/day group had total litter loss on lactation day 0 and one female in the 75 mg/kg bw/day group had total litter loss on lactation day 2. All other reproductive phase females survived to the scheduled necropsy. There were no test article-related clinical findings in the reproductive phase females.

Additionally, test substance-related effects on reproductive performance (fertility indices) were observed in the 250 mg/kg bw/day group males and reproductive phase females. Male and female fertility indices were 60.0% in this group compared to 90.0% in the control group. The mean number of days between pairing and coitus was increased in the 250 mg/kg bw/day group. Mean gestation length was increased in the 75 mg/kg bw/day group and in the single female in the 250 mg/kg bw/day group that delivered.

Of the nine reproductive phase females in the 250 mg/kg bw/day group with evidence of mating, three were nongravid and five had entirely resorbed litters. Only one female in this group delivered, but all pups were found dead on postnatal day (PND) 0, precluding evaluation of pup body weights (WIL Research Laboratories, 2005).

Effects on developmental toxicity

Description of key information

In a Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test, conducted according to OECD Test Guideline 422 and in compliance with GLP, the NOAEL for developmental effects was 75 mg/kg bw/day based on effects at the highest dose level of 250 mg/kg bw/day (WIL Research Laboratories, 2005).

Link to relevant study records
Reference
Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2005
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
GLP compliance:
yes
Species:
rat
Strain:
Crj: CD(SD)
Details on test animals or test system and environmental conditions:
ANIMAL RECEIPT AND ACCLIMATION
One hundred female and fifty male, sexually mature Crl:CD®(SD)IGS BR rats were received from Charles River Laboratories, Inc., Raleigh, North Carolina on April 27, 2004. The animals were 57 days old upon receipt. Each animal was examined by a qualified technician on the day of receipt, sexed and weighed 1 day after receipt. Each rat was uniquely identified by a Monel® metal eartag displaying the animal number and housed for 15 days for acclimation purposes. During the acclimation period, the rats were observed twice daily for general changes in appearance or behavior. The animals were allowed a pretreatment week during which they did not receive the test article but their clinical conditions and body weight and food consumption data were recorded during that time.

ANIMAL HOUSING
Upon arrival and until pairing, all animals were individually housed in clean, stainless steel wire-mesh cages suspended above cage-board. The cage-board was changed three times per week. The reproductive phase females were paired for mating in the home cage of the toxicity phase male of the same treatment group. Following positive evidence of mating, the reproductive phase females were individually housed in plastic maternity cages with nesting material, ground corncob bedding (Bed-O'Cobs®; The Andersons, Industrial Products Division, Maumee, Ohio). The nesting material is periodically analyzed by the manufacturer for contaminants. No contaminants were present in the bedding at concentrations sufficient to interfere with the outcome of the study. The results of these analyses are maintained at WIL Research Laboratories, LLC. The females were housed in these cages through lactation day 4, the scheduled day of necropsy. Females for which there was no evidence of mating were placed in plastic maternity cages with nesting material upon completion of a 14-day mating period. Females that did not deliver were necropsied on post-mating day 25. Animals were housed in accordance with the Guide for the Care and Use of Laboratory Animals (National Research Council, 1996). The animal facilities at WIL Research Laboratories, LLC are accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC International).

DIET, DRINKING WATER AND MAINTENANCE
The basal diet used in this study, PMI Nutrition International, LLC, Certified Rodent LabDiet® 5002, is a certified feed with appropriate analyses performed by the manufacturer and provided to WIL Research Laboratories, LLC. Feeders were changed and sanitized once per week. Municipal water supplying the facility is sampled for contaminants according to standard operating procedures. The results of the diet and water analyses are maintained at WIL Research Laboratories, LLC. No contaminants were present in animal feed or water at concentrations sufficient to interfere with the objectives of this study. The basal diet and reverse osmosis-purified (on-site) drinking water, delivered by an automatic watering system were provided ad libitum throughout the acclimation period and during the study.

ENVIRONMENTAL CONDITIONS
All rats were housed throughout the acclimation period and during the study in an environmentally controlled room. The room temperature and humidity controls were set to maintain daily averages of 71 ± 5°F (22 ± 3°C) and 50 ± 20% relative humidity. Room temperature and relative humidity were monitored using the Metasys DDC Electronic Environmental control system and were recorded approximately hourly. These data are summarized in Appendix B. Actual mean daily temperature ranged from 69.9°F to 75.2°F (21.1°C to 24.0°C) and mean daily relative humidity ranged from 39.0% to 48.9% during the study. Light timers were calibrated to provide a 12-hour light (6 a.m. to 6 p.m.)/12-hour dark photoperiod. The 12-hour light/12-hour dark photoperiod was interrupted as necessary to allow for the performance of protocol-specified activities. Air handling units were set to provide approximately 10 fresh air changes per hour.
Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
The vehicle and test article formulations were administered orally by gavage, via 15-gauge, polypropylene-shafted silicone-bulb-shaped-tipped dosing cannulae (Instech Solomon, Plymouth Meeting, Pennsylvania) once daily.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Prior to the initiation of dosing (May 5, 2004), representative control and test article formulations were prepared. Duplicate samples (1 mL each) for homogeneity determination were collected from the top, middle and bottom strata of the 25, 75 and 250 mg/kg bw/day dosing formulations and from the middle stratum of the control group preparation. The aliquots dispensed for homogeneity were representative of the size of aliquots dispensed for daily dosing procedures and included resuspension analysis over the longest period of aliquot storage. Samples from the control formulation and samples from the top and bottom strata were withdrawn from the aliquots after 6 and 12 days of refrigerated storage to confirm resuspension homogeneity and stability of the test article in the formulations. Fourteen-day refrigerated stability was assessed by comparison of the test article concentrations from samples collected from the middle stratum of each formulation on the day of preparation and following 14 days of storage. Duplicate samples (1 mL each) were collected from the middle stratum of each formulation, including the control group, for study weeks 0, 1, 2, 4 and 6 for confirmation of concentration. Characterization of the test article structure was performed by gas chromatography (GC) with mass selective detection (MSD). The determination of vinyl-tris(2-methoxyethoxy)silane in dried/deacidified corn oil formulations was performed by gas chromatography (GC) with mass selective detection (MSD).
Details on mating procedure:
Following a minimum of 14 days of treatment, one female assigned to the reproductive toxicity phase was cohabited with one male rat of the same treatment group. The selected males and females were approximately 12 weeks old when paired for mating. Animals were selected for pairing based on ear tag number; the male with the lowest animal number was paired with the female in the same dose group with the lowest animal number, continuing in increasing numerical eartag order until all animals were paired. A breeding record containing the male and female identification numbers and start of cohabitation was prepared. Positive evidence of mating was confirmed by the presence of a vaginal copulatory plug or the presence of sperm in a vaginal lavage. Each mating pair was examined daily. The day on which evidence of mating was identified was termed gestation day 0, and the animals were separated. A maximum of 14 days was allowed for mating. Females that had not shown evidence of mating in 14 days were placed in plastic maternity cages containing nesting material.
Duration of treatment / exposure:
Exposure period: 28 days
Four groups of male and female Crl:CD(SD)IGS BR rats (10/sex/group) were administered the test article, vinyl-tris(2-methoxyethoxy)silane, in the vehicle, dehydrated, deacidified corn oil, daily by oral gavage for 28 days; the males were treated 14 days prior to mating and continuing throughout mating. Additionally, four groups of female rats (10 per group) were mated with the treated males and were also administered the test article by oral gavage daily for a minimum of 14 days prior to mating, throughout mating and gestation and continuing through lactation day 3.
Frequency of treatment:
daily
Duration of test:
Premating exposure period (males): 14 days
Premating exposure period (females): 14 days
Duration of test: 14 days prior to mating, throughout mating and gestation and continuing through lactation day 3
Dose / conc.:
25 mg/kg bw/day (nominal)
Dose / conc.:
75 mg/kg bw/day (nominal)
Dose / conc.:
250 mg/kg bw/day (nominal)
No. of animals per sex per dose:
10/sex/dose
Control animals:
yes, concurrent vehicle
Details on study design:
Four groups of male and female Crl:CD (SD)IGS BR rats (10/sex/group) were administered the test article, vinyl-tris(2-methoxyethoxy)silane, in the vehicle, dehydrated, deacidified corn oil, daily by oral gavage for 28 days; the males were treated 14 days prior to mating and continuing throughout mating. Additionally, four groups of female rats (10 per group) were mated with the treated males and were also administered the test article by oral gavage daily for a minimum of 14 days prior to mating, throughout mating and gestation and continuing through lactation day 3. Dose levels were 0, 25, 75 and 250 mg/kg/day for the mated males, unmated females (toxicity phase) and mated females (reproductive phase).
Maternal examinations:
All animals were observed twice daily for appearance and behavior. Clinical observations, body weights and food consumption were recorded at appropriate intervals. For females that delivered or had macroscopic evidence of implantation, the numbers of former implantation sites and corpora lutea were recorded. Recognizable fetuses for the females euthanized in extremis were examined externally and preserved in 10% neutral-buffered formalin. For females that failed to deliver, a pregnancy status was determined.Uteri with no macroscopic evidence of implantation were opened and subsequently placed in a 10% ammonium sulfide solution for detection of early implantation loss
Ovaries and uterine content:
Uteri with no macroscopic evidence of implantation were opened and subsequently placed in a 10% ammonium sulfide solution for detection of early implantation loss
Fetal examinations:
All reproductive phase females were allowed to deliver and rear their offspring to lactation day 4; surviving dams and pups were euthanized and examined on lactation day 4.On the day parturition was initiated (PND 0), the pups were sexed and examined for gross malformations, and the numbers of still born and live pups were recorded. Individual gestation length was calculated using the date delivery started. Abnormal behavior of the offspring was recorded. The dam and litter remained together until PND 4. Intact offspring dying from PND 0 to 4 were necropsied. Cannibalized pups were discarded without necropsy. Tissues were preserved in 10% neutral-buffered formalin for possible future histopathologic examination only as deemed necessary by gross findings. The carcass of each pup was then discarded.
Statistics:
Mating, fertility, copulation and conception indices were analyzed using the Chi-square test with Yates’ correction factor (Hollander and Wolfe, 1999). Mean litter proportions (percent per litter) of pup viability and percent males at birth were subjected to the Kruskal-Wallis nonparametric ANOVA test to determine intergroup differences (Kruskal and Wallis, 1952). If the ANOVA revealed statistically significant (p<0.05) intergroup variance, the Mann-Whitney U-test (Kruskal and Wallis, 1952) was used to compare the test article-treated groups to the control group.
Indices:
Male (Female) Mating Index (%)
Male Fertility Index (%)
Male Copulation Index (%)
Female Fertility Index (%)
Female Conception Index (%)
On the day parturition was initiated (PND 0), the pups were sexed and examined for gross malformations, and the numbers of still born and live pups were recorded.

Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
There were no test substance-related clinical findings in the reproductive phase females.
Dermal irritation (if dermal study):
not examined
Mortality:
mortality observed, non-treatment-related
Description (incidence):
In the reproductive phase, one female in the 75 mg/kg bw/day group was euthanized in extremis on gestation day 22. The cause of moribundity for this female was considered to be dystocia. In addition, one female in the 250 mg/kg bw/day group had total litter loss on lactation day 0 and one female in the 75 mg/kg bw/day group had total litter loss on lactation day 2. All other reproductive phase females survived to the scheduled necropsy. There were no test article-related clinical findings in the reproductive phase females.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
There were no test substance-related effects on mean body weights and body weight gains during the pre-mating period in the reproductive phase females. However, mean gestation body weight gains were reduced in the 250 mg/kg bw/day group females throughout gestation; mean body weight on gestation day 20 was 22.1% lower than the control group value. Reductions in mean body weight and body weight gain late in gestation were attributed to the increased number (five of nine) of entirely resorbed litters in the 250 mg/kg bw/day group. Evaluation of lactation body weight in the 250 mg/kg/day group was precluded by reduced fertility, embryonic death and total litter loss. No test article-related effects on mean gestation or lactation body weight gains was observed in the 25 and 75 mg/kg/day group reproductive phase females.
Food consumption and compound intake (if feeding study):
effects observed, non-treatment-related
Description (incidence and severity):
There were no test article-related effects on mean food consumption during the pre-mating period in the reproductive phase in the 250 mg/kg bw/day group females.
Throughout gestation, a statistically significant reduction in the mean maternal food consumption was observed in the 250 mg/kg bw/day group. This was considered to depend on the poor reproductive performance and therefore, secondary to test substance.
No test article-related effects on mean gestation or lactation body weight gains were observed in the 25 and 75 mg/kg bw/day female group.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
Test substance-related decreases in the red and white blood cell parameters were observed in the 250 mg/kg bw/day male and female group. In these groups, the decreases in red blood cell indices were observed with mean red blood cell count, hemoglobin, hematocrit mean corpuscular hemoglobin concentration and percentage and absolute reticulocyte count. Additionally, there was a statistically significant decrease in the mean platelet counts and decreases in the mean white blood cell count, although not statistically significant, which were considered as test substance related. Furthermore, test substance related, statistically significant variations in white blood cell differential evaluation included decreases in basophils and eosinphils and an increase in monocytes.

In the 250 mg/kg bw/day male and female groups, changes in the granulocyte and erythrocoid series were observed. The myeloid:erythoid (M/E) ratio was decreased in males and females. Additionally, the percentages of myelocyte neutrophil, metamylocute neutrophil, band neutrophil, segmented neutrophil, eosinophil and total granulocytes were decreased in the 250 mg/kg bw/day male and groups. The relative percentages of rubriblasts, prorubriblasts, rubicytes, erythroid mitotic figures and total erythrocytes were increased in theses males and females. The increased percent erythrocytes in the bone marrow consisted of an increase in the erythroid proliferation pool (immature erythrocytes). This correlated with the decreases observed in red blood cell count, hemoglobin and hematocrit. No evidence of a reticulocytosis was evidenced supportive of a non-regenerative response at the peripheral level. However, review of bone marrow histopathology showed minimal to mild hypoplasia in some of the animals in the 250 mg/kg bw/day. Therefore, the relevance or mechanism for the cytologic changes cannot be determined.

Statistically significant decreases in mean hematocrit and hemoglobin were observed in the 250 mg/kg bw/day male group and in hemoglobin in the 75 mg/kg bw/day male group. Furthermore, decreased mean activated partial thromboplastin time was observed as well as an increase in the percent prorubricytes in the bone marrow in the 75 mg/kg bw/day male group. However, there was no dose response and/or only small variations from the control values occurred and consequently, these changes were considered as not test substance related.

Statistically significant increased prothrombin time in the 250 mg/kg bw/day female group and increased mean corpuscular volume the 25 and 75 mg/kg bw/day female groups were observed. However, these changes were not considered as test substance-related.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
A statistically significant decreased mean albumin, total protein and globulin levels and increased mean albumin/globulin ratio was noted in the 250 mg/kg bw/day male and female groups. These changes were considered as test substance related effects. Furthermore, statistically significant increased mean bilirubin level in the 250 mg/kg bw/day and mean chloride levels in the 25 and 75 mg/kg bw/day male groups occurred. Decreased mean blood urea nitrogen levels were observed in the 25 and 75 mg/kg bw/day female groups. These changes were not considered as adverse effects since there was not a dose response and similar trend in the opposite sex or small variations compared to control occurred.
Urinalysis findings:
not examined
Behaviour (functional findings):
no effects observed
Description (incidence and severity):
There were no test substance related findings at any dose groups.
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
Mean absolute and relative (to final body and brain weight) thymus and adrenal gland weights were observed in the 75 and 250 mg/kg bw/day male groups and in 250 mg/kg bw/day female group. These were reduced in a dose-related manner compared to the control group values. The differences were statistically significant in the 250 mg/kg bw/day group and correlated with the microscopic finding of lymphoid depletion. There were no microscopic correlates in the 25 and 75 mg/kg bw/day dose groups why the changes were not considered as adverse in these dose groups.

Mean absolute and relative thymus weights were decreased in the 75 and 250 mg/kg bw/day in females. However, since the decrease at 250 mg/kg bw/day was statistically significant only and correlated with lymphoid depletion. Therefore, the decrease at 250 mg/kg bw/day was considered as test substance-related only.

Statistically significant mean absolute and relative (to final body and brain weight) prostate weight in the 75 and 250 mg/kg bw/day groups were reduced in a dose-related manner compared to the control group values. Mean absolute and relative (to final body and brain weights) adrenal gland, right and left testis, right and left epididymis and seminal vesicle weighs were reduced in the 250 mg/kg bw/day. With the exception of the mean absolute and relative seminal vesicle weights, the differences from the control group were statistically significant. The reductions in male reproductive organ weights correlated with reduced fertility and microscopic findings in the 250 mg/kg bw/day group. A histological correlation for decreases in mean adrenal gland weight was not observed. No other test-substance related changes were observed.

In the 250 mg/kg bw/day dose male group, mean absolute or relative (to final body weight) brain, liver, kidney and thyroid/parathyroid weights were reduced compared to the control group values. Although not statistically significant, the 8 % decrease in mean final body weight in this group compared to the control group appears to be most likely explanation for these decreased organ weights. However, in the absence of a dose response, similar changes in the females or histopathological alterations to correlate with the weight decreases, the changes were not considered to be test substance related.
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
Test substance-related changes were observed in the testes, epididymides and thymus in the 250 mg/kg bw/day and changes in the spleen was noted in the 75 and 250 mg/kg bw/day groups. Small and soft epididymides and/or testes were observed in all the 250 mg/kg bw/day male group. Small thymus was observed in 9 of 10 animals in the 250 mg/kg bw/day group. These changes correlated with decreased reproductive organ and thymus weight noted for males in this group. In the spleen, adhesions or white areas were observed in 2 of 10 males in the 75 mg/kg bw/day and 5 of 10 males in the 250 mg/kg bw/day group.

Test substance-related changes were observed in the thymus and spleen were observed in the 250 mg/kg bw/day female group. Small thymus was observed in 3 of 10 animals in the 250 mg/kg bw/day. Additionally, adhesions or white areas in the spleen were observed in the 3 of 10 animals in the 250 mg/kg bw/day.

All other changes were considered to be spontaneous and/or incidental and therefore, unrelated to the test substance. Although pale pancreas was observed in the 250 mg/kg bw/day male group only, the finding was not considered as test substance related due to the absence of histologic correlation.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
In the 250 mg/kg bw/day dose male group, minimal to mild hypocellularity of the sternal bone marrow was observed in 5 of 10 males and in 2 of 10 females; aggregates of mature granulocytes were absent from histologic sections of the affected marrow; in the thymus, minimal to moderate lymphoid depletion was observed in 7 of 10 males and 3 of 10 females which correlated to reduced thymus gland weights; mild lymphoid depletion of the mandibular (3 of 9 males and 5 of 10 females) and/or mesenteric lymph nodes (5 of 10 males and 3 of 10 females). These changes were considered as test substance-related. In the 250 mg/kg bw/day female group, 2 animals had lymphoid depletion in the mesenteric lymph node although this was not considered as test substance related since the thymus and mandibular lymph nodes were unaffected.

In the 250 mg/kg bw/day dose female group, minimal to mild hypocellularity of the sternal bone marrow was observed in 2 of 10 animals. Aggregates of mature granulocytes were absent from histologic sections of the affected marrow. Hypocellularity of the bone marrow was considered a consistent finding with the hematology alterations.

In the spleen, capsular fibrosis was observed in 4 of 10 males and 3 of 10 females in the 250 mg/kg bw/day male group. This change was noted as adhesions to various abdominal structures or as white areas on the spleen. In contrast to the changes in hematopoietic cell numbers in the bone marrow and lymphoid depletion in the 250 mg/kg bw/day group in various tissues, red and white pulp components of the spleen appeared within normal limits. 2 males in the 75 mg/kg bw/day group had adhesions observed macroscopically although neither had capsular fibrosis.

In the testes, moderate to severe and bilateral seminiferous tubule degeneration was observed in 10 of 10 males in the 250 mg/kg bw/day male group. This correlated with decreased testicular organ weights, macroscopic findings (small and/or soft testes) and reduced fertility. Degeneration was characterised by a marked reduction or absence of spermatogeni epithelium. Minimal seminiferous tubule degeneration was observed in one control male and this was considered as incidental or background changes unrelated to treatment. Similarly, mild degeneration was observed in one male in the 25 mg/kg bw/day group and was associated with the absence of one epididymis which was considered as a spontaneous condition unrelated to the test substance.

Secondary to the extensive loss of spermatogenesis in the 250 mg/kg bw/day male group, all animals had mild to moderate hypospermia in the epididymides and 9 of 10 animals had luminal cellular debris. Hypospermia correlated to the decreased epididymal weights and macroscopic findings why it was considered as treatment related.

In the prostate, decreased section and/or atrophy was observed in 4 of 10; 6 of 10; 6 of 10 and 10 of 10 animals in the 0, 25, 75 and 250 mg/kg bw/day respectively. However, the number of animals within these groups having both decreased secretion and atrophy was 0 of 10; 1 of 10; 1 of 10 and 6 of 10 animals. The combination of these changes correlated with the decreased prostate weights in the 250 mg/kg bw/day group. Decreased secretion was characterised by extensive regions of acini devoid of eosinophilic secretory material (in the absence of free secretory material suggestive of post mortem/artefactual leakage) or small acini due to reduced amounts of secretory material often with a convoluted epithelial surface composed of enlarged cells. Atrophy was characterised by a similar reduction in secretory material, however, also by a marked thinning of the epithelium. Decreased secretion and atrophy were both considered as test substance related in the 250 mg/kg bw/day. it was unclear which change, atrophy or decreased secretion that was the largest contributor to the decreased prostate weights observed in the 250 mg/kg bw/day group. A histological correlation for the significantly reduced prostate weights in the 75 mg/kg bw/day group was unclear. However, the slightly increased incidence of atrophy in this group compared to the control group and finding mildly severe (compared to minimal) atrophy only in the 75 and 250 mg/kg bw/day groups, suggesting that prostatic atrophy may be the greater influence on the prostate weight decreased and may a test substance related change in the 75 mg/kg bw/day. No other test substance-related findings were observed.
Histopathological findings: neoplastic:
not examined
Other effects:
not examined
Number of abortions:
not specified
Pre- and post-implantation loss:
effects observed, treatment-related
Description (incidence and severity):
Only one female in the 250 mg/kg bw/day group delivered, however, had total litter loss on lactation day 0. This was considered as test substance related.
Total litter losses by resorption:
effects observed, treatment-related
Description (incidence and severity):
In the 250 mg/kg bw/day, only one female delivered pups, however, this female had total litter loss on lactation day 0. Due to the secere reproductive effects noted in this group, the total litter loss was considered to be test substance related. One female in the 75 mg/kg bw/day group had total litter loss on lactation dy 2, however, no macroscopic findings were present and therefore, not considered as test substance related.
Early or late resorptions:
effects observed, treatment-related
Description (incidence and severity):
5 of 9 females had entirely resorbed litters in the 250 mg/kg bw/day group.
Dead fetuses:
effects observed, treatment-related
Description (incidence and severity):
Only one female (of 10) in the 250 mg/kg bw/day group delivered, however, had total litter loss on lactation day 0. This was considered as test substance related.
Changes in pregnancy duration:
effects observed, treatment-related
Description (incidence and severity):
Mean gestation length was increased in the 75 mg/kg bw/day group and in the single female in the 250 mg/kg/day group that delivered.
Changes in number of pregnant:
effects observed, treatment-related
Description (incidence and severity):
Test article-related effects on reproductive performance (fertility indices) were observed in the 250 mg/kg bw/day group males and reproductive phase females. Male and female fertility indices were 60.0% in this group compared to 90.0% in the control group.
Other effects:
effects observed, treatment-related
Description (incidence and severity):
The mean number of days between pairing and coitus was increased in the 250 mg/kg bw/day group.
No animals in the 250 mg/kg bw/day female group survived to the lactation day 4 necropsy due to total litter loss or failure to deliver. In the 75 mg/kg bw/day group, the mean number of implantation sites was reduced compared to the control group although, not statistically significant. However, due to the severe reproductive effects observed in the 250 mg/kg bw/day group, the lower number of implantation sites in the 75 mg/kg bw/day group was considered as test substance related.
Dose descriptor:
NOAEL
Effect level:
75 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
clinical biochemistry
gross pathology
haematology
histopathology: non-neoplastic
organ weights and organ / body weight ratios
other: Test substance-related effects on reproductive performance.
Abnormalities:
effects observed, treatment-related
Localisation:
other: Test article-related effects on reproductive performance.
Fetal body weight changes:
no effects observed
Description (incidence and severity):
Pup body weights could not be evaluated since the pups were found dead on postnatal day 0. The mean body weights and body weight gains of pups in the 25 and 75 mg/kg bw/day groups were unaffected by maternal test substance administration.
Reduction in number of live offspring:
effects observed, treatment-related
Description (incidence and severity):
In the 250 mg/kg bw/day, only 1 of 10 females delivered pups, howeber, all 7 pups died on lactation day 0. In the 75 mg/kg bw/day, decreases in the mean numbers of pups and the live litter size on PND 0 was observed. These changes were considered as test-substance related. In the 25 mg/kg bw/day group, postnatal survival was unaffected.
Changes in sex ratio:
no effects observed
Description (incidence and severity):
The percentage of males per litter was similar to the control groups.
Changes in litter size and weights:
effects observed, non-treatment-related
Description (incidence and severity):
During PND 1 to 4, mean body weight gains in males and females in the 25 and 75 mg/kg bw/day groups were increased compared to the control group. Due to the decrease of the number of pups born in the 75 mg/kg bw/day, the increased weights in this group was conisdered to be secondary to this decrease.
Changes in postnatal survival:
effects observed, treatment-related
Description (incidence and severity):
Only one female in the 250 mg/kg bw/day group delivered, but all pups were found dead on postnatal day (PND) 0. Postnatal survival in the 75 mg/kg bw/day group was reduced throughout the lactation period (days 1-4), primarily due to one female with total litter loss on lactation day 2; the differences from the control group were not statistically significant but were considered test article-related. A slight increase was observed in the number of pups found dead or missing and presumed cannibalized in the 75 mg/kg bw/day group. No internal findings in the pups found dead or at the scheduled necropsy were attributed to maternal test article administration.
External malformations:
not examined
Skeletal malformations:
not examined
Visceral malformations:
no effects observed
Description (incidence and severity):
There were no soft tissue findings at 25 or 75 mg/kg bw/day groups.
Other effects:
not examined
Dose descriptor:
NOAEL
Effect level:
>= 75 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse teratogenicity effects
Dose descriptor:
NOAEL
Effect level:
75 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: fetotoxicity
Abnormalities:
no effects observed
Developmental effects observed:
yes
Lowest effective dose / conc.:
75 mg/kg bw/day (nominal)
Treatment related:
yes
Relation to maternal toxicity:
developmental effects occurring together with maternal toxicity effects, but not as a secondary non-specific consequence of maternal toxicity effects
Dose response relationship:
yes
Relevant for humans:
not specified
Conclusions:
In a developmental toxicity study, conducted according to OECD test guideline 422 and in compliance with GLP, a parental NOAEL was concluded to be 75 mg/kg bw/day based on adverse effects on the reproductive parameters. A NOAEL for fetotoxicity/developmental toxicity was concluded to be 75 mg/kg bw/day and for teratogenicity, a NOAEL of =75 mg/kg bw/day was concluded. It is unknown which role the reduced postnatal survival role might have for the developmental toxicity.
Effect on developmental toxicity: via oral route
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
75 mg/kg bw/day
Study duration:
subacute
Species:
rat
Effect on developmental toxicity: via inhalation route
Endpoint conclusion:
no study available
Effect on developmental toxicity: via dermal route
Endpoint conclusion:
no study available
Additional information

There are no full developmental toxicity tests available for tris(2-methoxyethoxy)vinylsilane. However, a Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test (OECD Test Guideline 422) is available which provides information regarding the potential of adverse developmental effects.

In the Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test, conducted according to OECD Test Guideline 422 and in compliance with GLP, four groups of male and female rats (10/sex/group) were administered tris(2 -methoxyethoxy)vinylsilane daily by oral gavage for up to 46 days. The males were treated 14 days prior to mating and continuing throughout the mating period. The females were mated with the treated males and were also administered the test substance daily by oral gavage for a minimum of 14 days prior and throughout mating, during gestation and until lactation day 3. Dose levels were 0, 25, 75 and 250 mg/kg bw/day. All animals were observed twice daily for appearance and behaviour. Clinical observations, body weights and food consumption were recorded at appropriate intervals. All reproductive phase females were allowed to deliver and rear their offspring to lactation day 4; surviving dams and pups were euthanized and examined on lactation day 4.

Of the nine reproductive phase females in the 250 mg/kg bw/day group with evidence of mating, three were non-gravid and five had entirely resorbed litters. Only one female in this group delivered, but all pups were found dead on postnatal day (PND) 0, precluding evaluation of pup body weights. In the 75 mg/kg bw/day group, the mean numbers of implantation sites, pups born and live litter size on PND 0 were reduced while the number of unaccounted for implantation sites was increased. These effects were considered test article-related, however, only the live litter size on PND 0 was statistically significantly different (p<0.01) from the control group. Postnatal survival in the 75 mg/kg bw/day group was reduced throughout the lactation period (day 14), primarily due to one female with total litter loss on lactation day 2. The differences from the control group were not statistically significant but were considered test substance-related. A slight increase in the number of pups found dead or missing and presumed cannibalized were observed in the 75 mg/kg bw/day group. The general physical condition and mean body weights and body weight gains of pups in the 25 and 75 mg/kg bw/day groups were unaffected by maternal test article administration. Clinical or macroscopic examinations of the offspring did not reveal any findings attributable to maternal test article administration in the 25 and 75 mg/kg bw/day groups. No internal findings in the pups found dead or at the scheduled necropsy were attributed to the maternal test substance administration. The NOAEL for foetotoxicity/developmental toxicity was concluded to be 75 mg/kg bw/day. A role for developmental toxicity in the reduced postnatal survival at this dose cannot be excluded. No teratogenic effects were observed (WIL Research Laboratories, 2005).  

Justification for classification or non-classification

Based on the Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test

, tris(2-methoxyethoxy)vinylsilane is classified for its potential to damage fertility and the unborn child (Repr. Cat 1B, reproductive and developmental toxicity, H360FD) according to Regulation (EC) No 1272/2008.

Additional information