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Toxicological information

Toxicity to reproduction

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Administrative data

Endpoint:
screening for reproductive / developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
06 January to 24 June 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report Date:
2010

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Test material form:
other: solution in arachis oil BP

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS

- Source: Han™: HsdRccHan™: WIST strain, obtained from Harlan Laboratories U.K. Ltd., Blackthorn, Bicester, Oxon, United Kingdom.

- Age at study initiation: 12 weeks.

- Weight at study initiation: Males 301-363 g; Females 199-230 g.

- Fasting period before study: Not reported.

- Housing: Initially, all animals were housed in groups of five in solid floor polypropylene cages with stainless steel mesh lids and softwood flake bedding (Datesand Ltd., Cheshire, UK). During the mating phase the animals were transferred to polypropylene grid floor cages suspended over trays lined with absorbent paper on a one male: one female basis. Following evidence of successful mating, the males were returned to their original cages. Mated females were housed individually during gestation and lactation, in solid floor polypropylene cages with stainless steel mesh lids and softwood flakes. Environmental enrichment was provided.

- Diet: A pelleted diet (Rodent 2018C Teklad Global Certified Diet, Harlan Laboratories U.K. Ltd., Oxon, United Kingdom) ad libitum.

- Water (e.g. ad libitum): Mains drinking water ad libitum.

- Acclimation period: 11 days.

ENVIRONMENTAL CONDITIONS

- Temperature (°C): 21±2°C.

- Humidity (%): 55±15%.

- Air changes (per hr): At least 15 changes per hour.

- Photoperiod (hrs dark / hrs light): 12 hours dark/12 hours light.

IN-LIFE DATES: From: Day 1 To: Day 43 (males); From: Day 1 To: Day 5 post partum (females). The first day of dosing was designated as Day 1 of the study.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
arachis oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: The test material was prepared at 30, 150 and 750 mg/kg bw/day as a solution in Arachis oil BP. The stability and homogeneity of the test material formulations were determined at the test laboratory. The formulations were shown to be stable for at least 25 days. Formulations were therefore prepared twice monthly and stored at approximately 4°C in the dark.

VEHICLE:

- Justification for use and choice of vehicle (if other than water): The test substance was stable for at least 25 days in Arachis oil BP and the prepared formulations were within ±6% of the nominal concentration.

- Amount of vehicle (if gavage): 4 ml/kg

Details on mating procedure:
On Day 15 of the exposure, animals were paired on a 1 male: 1 female basis within each dose group for a maximum of 14 days. Following evidence of mating (designated as Day 0 post coitum) the males were returned to their original cages and females were transferred to individual cages (completion of mating is during Week 6).
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Summary: The concentration of tri(isopropyl)silyl acrylate in the test material formulation was determined by gas chromatography (GC) using an external standard technique.

Samples: The test material formulations were extracted with methanol with final theoretical concentration of approximately 0.1 mg/ml.

Standards: Standard solutions of test material were prepared in methanol at a nominal concentration of 0.1 mg/ml.

Procedure: The sample and standard solutions were analysed by GC.

Homogeneity determinations: The test material formulations were assessed visually.

Stability determinations: The test material formulations were samples and analysed initially and then after storage at approximately 4°C in the dark for 25 days.

Verification of test material formulation concentrations: The test material formulations were sampled and analysed within 2 days of preparation.

Results: Mean measured concentrations were in the range 99-104% of nominal concentrations. The results showed that the formulation was stable for at least 25 days.
Duration of treatment / exposure:
From Day 1 to Day 42 (males); Day 1 to Day 4 post partum (females).
Frequency of treatment:
Once daily.
Details on study schedule:
- Age at mating of the mated animals in the study: At least 14 weeks of age.
Doses / concentrationsopen allclose all
Dose / conc.:
30 mg/kg bw/day (actual dose received)
Dose / conc.:
150 mg/kg bw/day (actual dose received)
Dose / conc.:
750 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
10 animals per sex per dose plus the control group.
Control animals:
yes, concurrent vehicle
Details on study design:
i) Groups of ten male and ten female animals were treated daily at the appropriate dose level throughout the study (except for females during parturition where applicable). The first day of dosing was designated as Day 1 of the study.

ii) On Day 15 animals were paired on a 1 male: 1 female basis within each dose group for a maximum of fourteen days.

iii) Following evidence of mating (presence of sperm in vagina and/or a copulation plug in the vagina; designated as Day 0 post coitum) the males were returned to their original cages and females were transferred to individual cages.

iv) Pregnant females were allowed to give birth and maintain their offspring until Day 5 post partum. Evaluation of each litter size, litter weight, mean offspring weight by sex, clinical observations and landmark developmental signs were also performed during this period.

v) The male dose groups were killed and examined microscopically on Day 43.

vi) At Day 5 post partum all females and surviving offspring were killed and examined macroscopically.

- Dose selection rationale: The dose levels were chosed based on the results of an oral repeated dose toxicity study in rats.
Positive control:
No.

Examinations

Parental animals: Observations and examinations:
CAGESIDE OBSERVATIONS/DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Immediately before dosing, soon after dosing and 1 and 5 hours after dosing during the working week. Animals were observed immediately before dosing, soon after dosing and 1 hour after dosing at weekends (except for females furing parturition where applicable).

- Cageside observations checked: Overt signs of toxicity, ill-health and behavioural changes.

BODY WEIGHT: Yes
- Time schedule for examinations: Individual bodyweights were recorded on Day 1 (prior to dosing) and then weekly for males until termination and weekly for females until mating was evident. Bodyweights were then recorded for females on Day 0, 7, 14 and 20 post coitum, and on Days 1 and 4 post partum.

FOOD CONSUMPTION: Yes
- During the maturation period, weekly food consumption was recorded for each cage of adults until pairing. This was continued for males after the mating phase. For females showing evidence of mating, food consumption was recorded for the periods covering post coitum Days 0-7, 7-14 and 14-20. For females with live litters, food consumption was recorded during the lactation period (Days 1-4).

FOOD EFFICIENCY: Yes
- Weekly food efficiency (bodyweight gain/food intake) was calculated for males and for females during the pre-mating phase. Due to offspring growth and milk production, food efficiency could not be accurately calculated during gestation and lactation.

WATER CONSUMPTION: Yes
- Time schedule for examinations: Water intake was observed daily by visual inspection of the water bottles for any overt changes. A possible treatment-related effect was detected therefore gravimetric measurements were initiated from Day 24 for males and during the gestation and lactation phases of the study for females.

PREGNANCY AND PARTURITION: Yes
- Each pregnant female was observed at approximately 08.30, 12.30 and 16.30 hours and around the period of expected parturition. Observations were carried out at approximately 08.30 and 12.30 hours at weekends and public holidays. The following was recorded for each female:
i) Date of pairing
ii) Date of mating
iii) Date and time of observed start of parturition
iv) Date and time of observed completion of parturition






Oestrous cyclicity (parental animals):
A vaginal smear was prepared for each female and the stage of oestrus or the presence of sperm was recorded.
Sperm parameters (parental animals):
Parameters examined in parental animals: testes weight, epididymis weight, the presence of sperm within the vaginal smears.
Litter observations:
STANDARDISATION OF LITTERS: Not performed.

PARAMETERS EXAMINED
The following parameters were examined in offspring:
Number of offspring born.
Numer of offspring alive recorded daily and reported on Days 1 and 4 post partum.
Sex of offspring on Days 1 and 4 post partum.
Clinical condition of offspring from birth to Day 5 post partum.
Individual offspring weights on Days 1 and 4 post partum (litter weights were calculated retrospectively from these data).
Surface righting reflex as a physical development.
Postmortem examinations (parental animals):
SACRIFICE
- Male animals: Adult males were killed by intravenous overdose of sodium pentobarbitone followed by exsanguination on Day 43.
- Maternal animals: Adult females were killed by intravenous overdose of sodium pentobarbitone followed by exsanguination on Day 5 post partum. Any females which failed to achieve pregnancy or produce a litter were killed on or after Day 26 post coitum.

GROSS NECROPSY
- All adult animals were subjected to a full external and internal examination, and any macroscopic abnormalities were recorded. For all females the uterus was examined for signs of implantation and the number of uterine implanations in each horn was recorded. This procedure was enhanced as necessary, by staining the uteri with a 0.5% ammonium polysulphide solution.

ORGAN WEIGHTS
- The epididymides and testes were removed from terminal kill makes, dissected free from fat and weighed before fixation.

HISTOPATHOLOGY
- Samples of the following tissues were preserved from all animals from each dose group, in buffered 10% formalin:
Coagulating gland, epididymides, ovaries, mammary tissue (female only), pituitary, prostate, seminal vesicles, testes, uterus/cervix and vagine.

All tissues were despatched to another test site in Switzerland for processing. The tissues from control and 750 mg/kg bw/day dose group animals which failed to mate or did no achieve pregnancy were prepared as paraffin blocks, sectioned at nominal thickness of 5 µm and stained with Haematoxylin and Eosin for subsequent microscopic examination. In addition, sections of testes and epididymides from all control and 750 mg/kg bw/day males were also stained with Periodic Acid-Schiff (PAS) stain and examined. Microscopic examination was conducted by the Study Pathologist.
Postmortem examinations (offspring):
POST MORTEM EXAMINATIONS (offspring)

GROSS EXAMINATION OF DEAD PUPS:
- Dying offspring during the study were subjected to a full external and internal examination, and any macroscopic abnormalities were recorded.

SACRIFICE
- Surviving offspring were terminated via intracardiac overdose of sodium pentobarbitone.

GROSS NECROPSY
- All offspring, including those dying during the study, were subjected to a full external and internal examination, and any macroscopic abnormalities were recorded.

HISTOPATHOLOGY/ORGAN WEIGHTS
- Not performed.
Statistics:
For males and females during the pre-mating phase, where appropriate, quantitative data were analysed by the Provantis™ Tables and Statistics Module. For each variable, the most suitable transformation of the data was found, the use of possible covariates checked and the homogeneity of means assessed using ANOVA and ANCOVA and Bartletts' test. The transformed data were analysed to find the lowest treatment level that showed a significant effect, using the WIlliams Test for parametric data or the Shirely Test for non-parametric data. If no dose response was found, but the data showed non-homogeneity of means, the data were analysed by a stepwise Dunnett (parametric) or Steel (non-parametric) test to determin significant differences from the control group. Finally, if required, pair-wise tests were performed using the Student t-test (parametric) or the Mann-Whitney 'U' test (non-parametric). Data for females during gestation and lactation and offspring data were assessed for dose response relationships by linear regression analysis, followed by one way analysis of variance (ANOVA) incorporating Levene's test for homogeneity of variancve. Where variances were shown to be homogenous, pairwise comparisons were conducted using Dunnett's test. Where Levene's test showed unequal variances the data were analysed using non-parametric methods: Kruskal-Wallis ANOVA and Man-Whitney 'U' test. Non-parametric methods were also used to analyse implantation loss, offspring sex ratio and landmark developmental markers.

Probability values (P) are presented as follows:
P<0.001***
P<0.01**
P<0.05*
P≥0.05 (not significant)
Reproductive indices:
i) Pre-coital Interval
Calculated as the time elapsing between initial pairing and the observation of positive evidence of mating.

ii) Fertility indices
For each group the following were calculated:

Mating Index (%) = (Number of animals mated ÷ Number of animals paired) x 100

Pregancy Index (%) = (Number of pregnant females ÷ Number of animals mated) x 100

Gestation and Parturition Data

The following parameters were calculated for individual data during the gestation and parturition period of the parental generation:

i) Gestational Length
Calculated as the number of days of gestation including the day for observation of mating and the start of parturition.

ii) Parturition Index
The following was calculated for each group:

Parturition Index (%) = (Number of females delivering live offspring ÷ Number of pregnant females ) x 100
Offspring viability indices:
The standard unit of assessment was considered to be the litter, therefore values were first calculated for each litter and the group mean was calculated using their individual litter values. Group mean values included all litters reared to termination (Day 5 of age).

i) Implanatation Losses (%)

Group mean percentile pre-implantation and post-implantation losses were calculated for each female/litter as follows:

% pre-implantation loss = [(Number of corpora lutea - Number of implantation sites) ÷ Number of corpora lutea] x 100

% post-implantation loss = [(Number of implantation sites - Total number of offspring born) ÷ Number of implantation sites] x 100

ii) Live Birth and Viability Indices

The following indices were calculated for each litter as follows:

Live Birth Index (%) = (Number of offspring alive on Day 1 ÷ Number of offspring born) x 100

Viability Index (%) = (Number of offspring alive on Day 4 ÷ Number of offspring alive on Day 1) x 100

iii) Sex Ratio (% males)

Sex ratio was calculated for each litter value on Day 1 and 4 post partum, using the following formula:

(Number of male offspring ÷ Total number of offspring) x 100

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Increased salivation was detected soon after and one hour after dosing for animals of either sex treated with 750 mg/kg bw/day, with the effect extending into the 150 mg/kg bw/day dose group. This was also occasionally observed up to five hours after dosing in animals of either sex treated with 750 mg/kg bw/day, and isolated instances of increased salivation prior to dosing were also observed for males treated with 750 mg/kg bw/day and for one female treated with 150 mg/kg bw/day.
One female treated with 750 mg/kg bw/day showed red fluid around the snout and mouth, lachrymation and chromodacryorrhea on Day 29. Complete regression was evident thereafter and, as such, this isolated finding was considered to have arisen incidentally and was not considered to represent systemic toxicity. Remaining clinical signs were confined to incidents of generalised fur loss observed for one female treated with 750 mg/kg bw/day and two females treated with 150 mg/kg bw/day. This observation was also noted for one control female. Red/brown staining around the mouth was also evident for one female treated with 750 mg/kg/day. These observations are occasionally observed in laboratory maintained animals and are unrelate to treatment with the test material.
Mortality:
no mortality observed
Description (incidence):
There were no unscheduled deaths during the study.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Males treated with 750 mg/kg bw/day showed actual body weight losses during the premating phase of the study and statistically significant reductions in body weight gains when compared to controls during the treatment period (P<0.05 - P<0.01). The reduction in body weight gains during the treatment period extended into the male 150 mg/kg bw/day dose group, with statistically significant reduction observed during Week 3 (P<0.01).
Body weight losses were also evident for females treated with 750 mg/kg bw/day during the first week of the treatment, resulting in statistically significant reductions in body weight gains oserved during the first week of treatment when compared to controls (P<0.05). Females treated with 150 mg/kg/day also showed statistically significant reductions in body weight gains in comparison to control values during the first week of treatment (P<0.05). Reduced body weight gains were also evident during Week 2 for females treated with 750 and 150 mg/kg bw/day. Females treated with 750 mg/kg bw/day showed statistically significant reductions in body weight gains in comparison to control values during the final week of the gestation phase (P<0.01). Cumulative body weight gains during the overall gestation phase were therefore lower for high dose females when compared to controls (P<0.01). During the lactation phase, females treated with 750 mg/kg bw/day showed a statistically significant increase in body weight gains compared to controls (P<0.01). Similar increases in body weight gains were also evident for females treated with 150 mg/kg bw/day (P<0.05).
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
A reduction in dietary intake was evident for animals of either sex treated with 750 mg/kg bw/day during the first two weeks of the study. Food conversion efficiency (the ratio of body weight gain to dietary intake) was also reduced for females treated with 750 mg/kg bw/day during the pre-mating phase, and for males treated at the highest dose level throughout the treatment period (with the exception of the mating phase when food consumption was not recorded). Slight reductions in dietary intake were also evident for males treated with 150 mg/kg bw/day during the treatment period, when compared to controls, and for females treated with 150 mg/kg bw/day during the pre-mating phase. Food conversion efficiencies were similarly affected. Slight reductions in dietary intake were also evident for females treated with 750 and 150 mg/kg bw/day during the first week of the gestation period, and for females treated with 750 mg/kg bw/day during the lactation period, although statistical analysis of the data did not reveal any significant intergroup differences.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Description (incidence and severity):
Daily visual inspections of water bottles revealed an increase in water intake at the highest dose level. Daily measurements were therefore initiated. Higher water intake was clearly evident for males treated with 750 mg/kg bw/day when compared to controls thereafter. Increased water intake was also evident for females treated with 750 mg/kg bw/day during the gestation period, although statistical significance was only achieved on Day 9 (P<0.01). Increases were also observed on Day 2 of lactation, however statistical significance was not achieved.
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
Histopathological examinations did not reveal any treatment-related effects. The few microscopic findings recorded were the stages of oestrus cycle in the vagina, the functional status in the mammary gland and exfoliation of the mucosal epithelium, in the stomach of one control female. The findings in the vagina and mammary gland corresponded to the physiological reproductive status. The origin of exfoliation of gastric mucosa, accompanied by aggregates of pollen from the diet, was not clear from this study but was considered to be of no toxicological importance.
Histopathological findings: neoplastic:
not examined
Other effects:
not examined

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:
no effects observed
Reproductive function: sperm measures:
no effects observed
Reproductive performance:
no effects observed
Description (incidence and severity):
MATING
No treatment-related effects were detected in mating performance for treated animals when compared to controls.

FERTILITY
One female treated with the highest dose level did not produce a pregnancy following successful mating. All remaining females from the treated and control groups achieved pregnancy and delivered offspring.

GESTATION LENGTH
No treatment-related effects were detected in the length of gestation between control and treated groups. Statistical analysis of the gestation length data did not reveal any significant intergroup differences.
One female treated with 30 mg/kg/day showed a gestation length of 25 days. A total litter loss was subsequently observed for this animal. This is a low incidence finding occasionally observed in reproductive studies and, in isolation, was considered not to be related to treatment.

Effect levels (P0)

open allclose all
Dose descriptor:
NOAEL
Remarks:
systemic toxicity
Effect level:
750 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Treatment-related effects in adults (increased salivation, reduced body weight gain) were not considered to be adverse.
Dose descriptor:
NOAEL
Remarks:
reproductive toxicity
Effect level:
750 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: There were no adverse effects on fertility at the highest dose level tested.

Results: F1 generation

General toxicity (F1)

Clinical signs:
no effects observed
Description (incidence and severity):
No treatment-related clinical signs were observed. The number of decedents was higher at 750 mg/kg bw/day compared to the remaining dose groups. THis was due to the two litter losses observed at this dose level.
Mortality / viability:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Reduced total litter weights were evident at 750 mg/kg bw/day when compared to controls, with a statistically significant reduction observed on Day 4 when compared to controls, with a statistically significant reduction observed on Day 4 when compared to controls (P<0.001). Mean bod weights for offspring were comparable to controls on Day 1 of lactation, although reduced mean body weight gains were observed for male and female offspring from the 750 mg/kg bw/day litters compared to those from the control litters (P<0.001 and P<0.01, respectively).
Food consumption and compound intake (if feeding study):
not examined
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
Description (incidence and severity):
No treatment-related macroscopic abnormalities were detected for offspring dying during lactation or at termination on Day 5 post-partum. The number of offspring deaths on the day of parturition at 750 mg/kg bw/day was higher than the interim deaths from the other treatment levels and the controls. The findings observed in the interim death offspring were those occasionally observed in reproductive studies of this type and were considered to be unrelated to toxicity of the test material. No treatment-related macroscopic abnormalities were detected for offspring at terminal kill. Macroscopic findings observed at termination were considered to be low incidence findings occasionally observed in reproductive studies of this type, and not related to test material toxicity.
Histopathological findings:
not examined

Details on results (F1)

In total, ten females from the control and 150 mg/kg bw/day dose group, nine females treated with 30 mg/kg bw/day and seven females treated with 750 mg/kg bw/day gave birth to a live litter and successfully reared young to Day 5 of age. One female treated with 750 mg/kg bw/day failed to achieve pregnancy following evidence of mating and two females treated at this dose level showed a total litter loss after parturition. A total litter loss was also evident for one female treated with 30 mg/kg bw/day. The following assessmen of litter response is based on all litters reared to termination on Day 5 of lactation, where applicable.

LITTER SIZE AND VIABILITY
Slightly lower numbers of corpora lutea, implantation sites and litter sizes at birth were evident at 750 mg/kg bw/day when compared to controls. Slightly higher post-implantation losses were also observed at 750 mg/kg bw/dday when compared to controls and two litters showed a total litter loss at 750 mg/kg bw/day. Statistical analysis of the data did not reveal any significant intergroup differences. The number of offspring deaths on the day of parturition at 750 mg/kg/ bwday was higher than the interim deaths from the other treatment levels and controls. A total litter loss was observed at 30 mg/kg bw/day but this is occasionally observed in reproductive studies and was considered to be incidental.

Effect levels (F1)

Dose descriptor:
NOAEL
Remarks:
developmental toxicity
Generation:
F1
Effect level:
150 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Reduced litter weights, reduced mean body weight gains and litter size of offspring. The reviewer considers these effects to be secondary to maternal toxicity, specifically reduced body weight gains.

Overall reproductive toxicity

Reproductive effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
The oral administration of tri(isopropyl)silyl acrylate to rats by gavage in an OECD 421 screening study conducted to GLP (reliability score 1), at dose levels of 750, 150 and 30 mg/kg/day resulted in treatment-related effects at 750 and 150 mg/kg/day and therefore a clear 'No Observed Effect Level' (NOEL) was established at 30 mg/kg/day. The effects detected in the adults were considered not to represent an adverse effect. The 'No Observed Adverse Effect Level' (NOAEL) for systemic toxicity was therefore considered to be 750 mg/kg/day. There were no adverse effects on fertility or other reproductive parameters of the parent generation therefore the NOAEL for reproductive toxicity was considered to be at least 750 mg/kg/day by the author of this summary. Treatment-related effects were detected in litters (reduced litter weights, reduced mean bodyweight gains and reduced litter size) from the 750 mg/kg/day therefore the NOAEL for developmental toxicity was considered to be 150 mg/kg/day for reproductive toxicity. The observed effects were considered to be secondary to maternal toxicity, specifically body weigh gain changes.