Isobutyric acid, monoester with 2,2,4-trimethylpentane-1,3-diol

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Propanoic acid, 2-methyl-, monoester with 2,2,4-trimethyl-1,3-pentanediol

IUPAC Name:

Propanoic acid, 2-methyl-, monoester with 2,2,4-trimethyl-1,3-pentanediol

Constituent 2

Reference substance name:

Isobutyric acid, monoester with 2,2,4-trimethylpentane-1,3-diol

EC Number:

246-771-9

EC Name:

Isobutyric acid, monoester with 2,2,4-trimethylpentane-1,3-diol

Cas Number:

25265-77-4

Molecular formula:

C12H24O3

IUPAC Name:

3-hydroxy-2,2,4-trimethylpentyl 2-methylpropanoate

Constituent 3

Reference substance name:

(3-hydroxy-2,2,4-trimethylpentyl) 2-methylpropanoate

IUPAC Name:

(3-hydroxy-2,2,4-trimethylpentyl) 2-methylpropanoate

Constituent 4

Reference substance name:

Texanol Ester-Alcohol; TEXANOL; 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate

IUPAC Name:

Texanol Ester-Alcohol; TEXANOL; 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate

Details on test material:

-Name of test material (as cited in study report): Isobutyric acid, 2,2,4-trimethyl-1,3-pentanediol monoester, mixed isomers

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST SYSTEM, ANIMAL RECEIPT, AND ACCLIMATION
Sexually mature, virgin female Sprague Dawley [Crl:CD(SD)] rats were used as the test system on this study. This species and strain of animal is recognized as appropriate for developmental toxicity studies. WIL Research has historical control data on the background incidence of fetal malformations and developmental variations in the Crl:CD(SD) rat. This animal model has been proven to be susceptible to the effects of developmental toxicants. The number of animals selected for this study was based on the United States EPA Health Effects Test Guidelines OPPTS 870.3700, Prenatal Developmental Toxicity Study, AUG-1998 and the OECD Guidelines for the Testing of Chemicals Guideline 414, Prenatal Developmental Toxicity Study, 22-JAN-2001, which recommend evaluation of approximately 20 females with implantation sites at necropsy. Given the possibility of nongravid animals, unexpected deaths, or treatment-related moribundity and/or mortality, this was an appropriate number of animals to obtain a sample size of 20 females at termination. Crl:CD(SD) rats (125 females) were received in good health from Charles River Laboratories, Inc., Raleigh, NC, on 08-APR-2014. The animals were approximately 79 days old upon receipt. Each female was examined by a qualified biologist on the day of receipt. The day following receipt, all animals were weighed and clinical observations were recorded. Each rat was uniquely identified by a Monel® metal ear tag displaying the animal number and housed for a minimum of 14 days for acclimation purposes. During the acclimation period, the rats were observed twice daily for mortality and changes in general appearance and behavior.

ANIMAL HOUSING
Upon arrival and until pairing, all rats were individually housed in clean, stainless steel wire-mesh cages suspended above cage-board. The cage-board was changed at least 3 times per week. The rats were paired for mating in the home cage of the male. Following positive evidence of mating, the females were returned to individual suspended wire-mesh cages; nesting material was not required as the females were euthanized prior to the date of expected parturition. Animals were maintained in accordance with the Guide for the Care and Use of Laboratory Animals (National Research Council, 1996). The animal facilities at WIL Research are fully accredited by AAALAC International. Enrichment devices were provided to all animals as appropriate throughout the study for environmental enrichment and to aid in maintaining the animals’ oral health, and were sanitized weekly.

DIET, DRINKING WATER, AND MAINTENANCE
The basal diet used in this study, PMI Nutrition International, LLC Certified Rodent LabDiet® 5002, was a certified feed with appropriate analyses performed by the manufacturer and provided to WIL Research. Feed lots used during the study were documented in the study records. The feeders were changed and sanitized once per week. Municipal water supplying the facility was sampled for contaminants according to WIL Research’s SOPs. The results of the diet and water analyses are maintained at WIL Research. No contaminants were present in animal feed or water at concentrations sufficient to interfere with the objectives of this study. Reverse osmosis-purified (on-site) drinking water, delivered by an automatic watering system, and the basal diet 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 relative humidity controls were set to maintain environmental conditions of 71°F ± 5°F (22°C ± 3°C) and 50% ± 20%, respectively. Room temperature and relative humidity data were monitored continuously and were scheduled for automatic collection on an hourly basis. Actual mean daily temperature ranged from 70.2°F to 70.7°F (21.2°C to 21.5°C) and mean daily relative humidity ranged from 44.3% to 52.2% during the study. Fluorescent lighting provided illumination for a 12-hour light (0600 hours to 1800 hours)/12-hour dark photoperiod. The light status (on or off) was recorded once every 15 minutes.

ASSIGNMENT OF ANIMALS TO TREATMENT GROUPS AND BREEDING PROCEDURES
At the conclusion of the acclimation period, all available females were weighed and examined in detail for physical abnormalities. At the discretion of the Study Director, each animal judged to be in good health and meeting acceptable body weight requirements was placed in a suspended wire-mesh cage with a resident male from the same strain and source for breeding. Resident males were untreated, sexually mature rats utilized exclusively for breeding. These rats were maintained under similar laboratory conditions as the females. A breeding record containing the male and female identification numbers and the dates of cohabitation was maintained. The selected females were approximately 13 weeks old when paired for breeding. Positive evidence of mating was confirmed by the presence of a vaginal copulatory plug or the presence of sperm in a vaginal lavage and verified by a second biologist. 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. The experimental design consisted of 3 test substance-dosed groups and 1 control group, composed of 25 rats per group. The bred females were assigned to groups using a WTDMS™ computer program which randomized the animals based on stratification of the gestation day 0 body weights in a block design. Animals not assigned to study were transferred to the WIL Research stock colony or euthanized by carbon dioxide inhalation
and discarded. Body weight values ranged from 222 g to 298 g on gestation day 0.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on exposure:

ORGANIZATION OF TEST GROUPS, DOSAGE LEVELS, AND TREATMENT REGIMEN
The vehicle and test substance formulations were administered orally by gavage, via an appropriately sized flexible, Teflon®-shafted, stainless steel ball-tipped dosing cannula, once daily during gestation days 1-19. The dosage volumes for the control, 100, 300, and 1000 mg/kg/day groups were 1.05, 0.11, 0.32, and 1.05 mL/kg, respectively. Individual dosages were based on the most recently recorded body weights to provide the correct mg/kg/day dose. All animals were dosed at approximately the same time each day.

Dosage levels were determined from the results of a previous combined repeated-dose and reproductive/developmental toxicity study in the rat (Faber and Hosenfeld, 1992). In that study, the no-observed-adverse-effect level (NOAEL) for subchronic toxicity was 1000 mg/kg/day and the no-observed-effect level (NOEL) for reproductive toxicity was 1000 mg/kg/day. The selected route of administration for this study was oral (gavage) because this is a potential route of human exposure. Historically, this route has been used extensively for studies of this nature.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

Gestation days 1-19

Frequency of treatment:

once daily

Duration of test:

20 days

No. of animals per sex per dose:

25

Control animals:

yes, concurrent vehicle

Examinations

Maternal examinations:

CLINICAL OBSERVATIONS AND SURVIVAL
All rats were observed twice daily, once in the morning and once in the afternoon, for moribundity and mortality. Individual clinical observations were recorded daily from gestation days 0 through 20 (prior to dose administration during the dosing period). Animals were also observed for signs of toxicity approximately 1 hour following dose administration. The absence or presence of findings was recorded for all animals.

BODY WEIGHTS AND GRAVID UTERINE WEIGHTS
Individual maternal body weights were recorded on gestation days 0-20 (daily). Group mean body weights were calculated for each of these days. Mean body weight changes were calculated for each corresponding interval and also for gestation days 1-3, 3-6, 6-9, 9-12, 12-16, 16-20, and 1-20.
Gravid uterine weight was collected and net body weight (the gestation day 20 body weight exclusive of the weight of the uterus and contents) and net body weight change (the gestation day 0-20 body weight change exclusive of the weight of the uterus and contents) were calculated and presented for each gravid female at the scheduled laparohysterectomy.

FOOD CONSUMPTION
Individual food consumption was recorded on gestation days 0-20 (daily). Food intake was reported as g/animal/day and g/kg/day for the corresponding body weight change intervals. When food consumption could not be determined for an animal during a given interval (due to a weighing error, food spillage, etc.), group mean values were calculated for that interval using the available data. The time periods when food consumption values were unavailable for a given animal were designated as “NA” on the individual report tables.

GESTATION DAY 20 LAPAROHYSTERECTOMY
Laparohysterectomies and macroscopic examinations were performed blind to treatment group. All females were euthanized on gestation day 20 by carbon dioxide inhalation. The thoracic, abdominal, and pelvic cavities were opened by a ventral mid-line incision, and the contents were examined. In all instances, the postmortem findings were correlated with the antemortem observations, and any abnormalities were recorded. The uterus and ovaries were then exposed and excised. The number of corpora lutea on each ovary was recorded. The trimmed uterus was weighed and opened, and the number and location of all fetuses, early and late resorptions, and the total number of implantation sites were recorded. The placentae were also examined. The individual uterine distribution of implantation sites was documented using the following procedure. All implantation sites, including resorptions, were numbered in consecutive order beginning with the left distal to the left proximal uterine horn, noting the position of the cervix, and continuing from the right proximal to the right distal uterine horn. Uteri with no macroscopic evidence of implantation were opened and subsequently placed in 10% ammonium sulfide solution for detection of early implantation loss (Salewski, 1964). Maternal tissues were preserved in 10% neutral-buffered formalin for possible future histopathologic examination only as indicated by the gross findings. The carcass of each female was then discarded.

Fetal examinations:

FETAL MORPHOLOGICAL EXAMINATION
Fetal examinations were performed blind to treatment group. Each viable fetus was examined externally, individually sexed, weighed, euthanized by a subcutaneous injection of sodium pentobarbital in the scapular region, and tagged for identification. Fetal tags contained the WIL Research study number, the female number, and the fetus number. The detailed external examination of each fetus included, but was not limited to, an examination of the eyes, palate, and external orifices, and each finding was recorded. Nonviable fetuses (if the degree of autolysis was minimal or absent) were examined, the crown-rump length measured, weighed, and tagged individually. Crown-rump measurements and degrees of autolysis were recorded for late resorptions, a gross external examination was performed (if possible), and the tissues were discarded. Each fetus was subjected to a visceral examination using a modification of the Stuckhardt and Poppe fresh dissection technique to include the heart and major blood vessels (Stuckhardt and Poppe, 1984). The sex of each fetus was confirmed by internal examination. Fetal kidneys were examined and graded for renal papillae development (Woo and Hoar, 1972). Heads from approximately one-half of the fetuses in each litter were placed in Bouin's fixative for subsequent soft-tissue examination by the Wilson sectioning technique (Wilson, 1965). The heads from the remaining one-half of the fetuses were examined by a midcoronal slice. All carcasses were eviscerated and fixed in 100% ethyl alcohol. Following fixation in alcohol, each fetus was stained with Alizarin Red S (Dawson, 1926) and Alcian Blue (Inouye, 1976). Fetuses were then examined for skeletal malformations and developmental variations. External, visceral, and skeletal findings were recorded as developmental variations (alterations in anatomic structure that are considered to have no significant biological effect on animal health or body conformity and/or occur at high incidence, representing slight deviations from normal) or malformations (those structural anomalies that alter general body conformity, disrupt or interfere with normal body function, or may be incompatible with life).

Statistics:

All statistical tests were performed using WTDMS™ unless otherwise noted. Analyses were conducted using two-tailed tests (except as noted otherwise) for minimum significance levels of 1% and 5%, comparing each test substance-dosed group to the control group. Each mean was presented with the standard deviation (S.D.), standard error (S.E.), and the number of animals (N) used to calculate the mean. Data obtained from nongravid animals were excluded from statistical analyses. Due to the use of significant figures and the different rounding conventions inherent in the types of software used, the means, standard deviations, and standard errors on the summary and individual tables may differ slightly. Therefore, the use of reported individual values to calculate subsequent parameters or means will, in some instances, yield minor variations from those listed in the report data tables. Where applicable, the litter was used as the experimental unit. Maternal body weights (absolute and net), body weight changes (absolute and net), and food consumption, gravid uterine weights, numbers of corpora lutea, implantation sites, and viable fetuses, and fetal body weights (separately by sex and combined) were subjected to a parametric one-way ANOVA (Snedecor and Cochran, 1980) to determine intergroup differences. If the ANOVA revealed significant (p<0.05) intergroup variance, Dunnett's test (Dunnett, 1964) was used to compare the test substance-dosed groups to the control group. Mean litter proportions (percent per litter) of prenatal data (viable and nonviable fetuses, early and late resorptions, total resorptions, pre- and postimplantation loss, and fetal sex distribution), total fetal malformations and developmental variations (external, visceral, skeletal, and combined) and each particular external, visceral, and skeletal malformation or variation were subjected to the Kruskal-Wallis nonparametric ANOVA test (Kruskal and Wallis, 1952) to determine intergroup differences.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
MATERNAL CLINICAL OBSERVATIONS AND SURVIVAL
All females in the control, 100, 300, and 1000 mg/kg/day groups survived to the scheduled necropsy on gestation day 20. Test substance-related clinical findings were observed at all dosage levels at the daily examinations and/or approximately 1 hour following dose administration during the dosing period. Limited occurrences of red material around the nose for females in the 100, 300, and 1000 mg/kg/day groups and yellow material around the urogenital area, primarily for females in the 1000 mg/kg/day group, were noted at the daily examinations and/or approximately 1 hour following dose administration. These findings were noted in single females as early as gestation day 2 and continued sporadically through the end of the dosing period. In addition, red and/or clear material around the mouth was noted for the majority of females in the 300 and 1000 mg/kg/day groups, and to a lesser extent in the 100 mg/kg/day group, approximately 1 hour following dose administration during the dosing period. These material findings were noted in a dose-dependent manner beginning as early as gestation day 1 and continued through the end of the dosing period. However, as all of the aforementioned findings occurred in single animals, in a manner that was not dose related, and/or did not generally persist to the daily examinations the following day, they were considered non-adverse. Other findings noted in the treated groups, including hair
loss on various body surfaces, occurred infrequently, at similar frequencies in the control group, and/or in a manner that was not dose-related.

MATERNAL BODY WEIGHTS AND GRAVID UTERINE WEIGHTS
Test substance-related, significantly (p<0.05 or p<0.01) lower mean body weight gains were noted in the 1000 mg/kg/day group during gestation days 1-3 and 3-6 compared to the control group. Mean body weight gains in this group were generally similar to the control group during the remainder of the dosing period (gestation days 6-9, 9-12, 12-16, and 16-20). However, mean body weight gain in the 1000 mg/kg/day group was significantly (p<0.01) lower than the control group when the entire dosing period (gestation days 1-20) was evaluated due to the initial lower mean body weight gains. Although not of sufficient magnitude to result in statistically significantly lower mean body weights during the dosing period, the initial lower mean body weight gains noted in the 1000 mg/kg/day group were considered adverse. A significantly (p<0.01) lower mean net body weight gain was noted in the 1000 mg/kg/day group compared to the control group, while mean net body weight and gravid uterine weight in this group were unaffected by test substance administration. Mean maternal body weights, body weight gains, net body weights, net body weight gains, and gravid uterine weights in the 100 and 300 mg/kg/day groups were unaffected by test substance administration. Differences from the control group were slight and not statistically significant.

MATERNAL FOOD CONSUMPTION
Maternal food consumption, evaluated as g/animal/day and g/kg/day, in the 1000 mg/kg/day group was significantly (p<0.01) lower than the control group during gestation days 1-3 and 3-6, corresponding to the lower mean body weight gains observed during these intervals. The lower mean food consumption was considered to be test substance-related and adverse. Mean food consumption in the 1000 mg/kg/day group was similar to the control group throughout the remainder of the dosing period (gestation days 6-9, 9-12, 12-16, and 16-20) and when the overall dosing period (gestation days 1-20) was evaluated. Significantly (p<0.05) lower mean food consumption (g/animal/day only) was also noted in the 1000 mg/kg/day group on gestation day 17-18 compared to the control group. This transient difference was not attributed to the test substance because there was no corresponding effect on body weight. Maternal food consumption in the 100 and 300 mg/kg/day groups was unaffected by test substance administration. Significantly (p<0.05 or p<0.01) higher mean food consumption was noted in the 300 mg/kg/day group on gestation days 13-14 (g/kg/day only), 19-20, and 16-20 (g/kg/day only) and significantly (p<0.05) lower mean food consumption was noted in this group during gestation days 1-3 (g/kg/day only). These transient differences were not attributed to the test substance because there were no corresponding effects on body weight at this dosage level.

MATERNAL NECROPSY DATA
At the scheduled necropsy on gestation day 20, no test substance-related internal findings were observed at dosage levels of 100, 300, and 1000 mg/kg/day. Macroscopic findings observed in the test substance-treated groups occurred infrequently, at similar frequencies in the control group, and/or in a manner that was not dose-related. Three, 4, and 1 females in the control, 100, and 300 mg/kg/day groups, respectively, were determined to be nongravid.

GESTATION DAY 20 LAPAROHYSTERECTOMY DATA
Intrauterine growth and survival were unaffected by test substance administration at dosage levels of 100, 300, and 1000 mg/kg/day. Parameters evaluated included postimplantation loss, live litter size, mean fetal body weights, and fetal sex ratios. Mean numbers of corpora lutea and implantation sites and the mean litter proportions of pre-implantation loss were similar across all groups. Differences from the control group were slight and not statistically significant.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

300 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Remarks on result:

not determinable

2

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Remarks on result:

not determinable

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
FETAL MORPHOLOGICAL DATA
The numbers of fetuses (litters) available for morphological evaluation were 340(22), 320(21), 352(24), and 376(25) in the control, 100, 300, and 1000 mg/kg/day groups, respectively. Malformations were observed in 3(2), 2(2), 3(3), and 2(2) fetuses (litters) in these same respective dosage groups and were considered spontaneous in origin.

EXTERNAL MALFORMATIONS AND VARIATIONS
There were no test substance-related external malformations noted for fetuses at any dosage level. Microphthalmia or anophthalmia was noted for 1(1), 2(2), and 1(1) fetuses (litters) in the control, 300, and 1000 mg/kg/day groups, respectively. Fetus no. 14043-02 in the 1000 mg/kg/day group had anophthalmia (left) and fetus nos. 13992-02 and 14037-10 in the 300 mg/kg/day group had microphthalmia (right or left; no apparent skeletal origin). Because these findings were noted in single fetuses, did not occur in a dose-related manner, the mean litter proportions were not statistically
significantly different from the concurrent control group and were within the WILResearch historical control data range, and/or were also noted in a control group fetus (no. 14015-14, anophthalmia [bilateral]; skeletally, orbit smaller than normal), they were not considered test substance-related. No other external developmental malformations were noted at any dosage level. There were no external developmental variations noted in fetuses at any dosage level.

VISCERAL MALFORMATIONS AND VARIATIONS
There were no test substance-related soft tissue malformations noted for fetuses at any dosage level. Soft tissue malformations were noted for 1 fetus each in the control, 100, and 1000 mg/kg/day groups. Lobular dysgenesis of the lungs (1 lobe present, bilateral) was noted for fetus no. 13986-12 in the 1000 mg/kg/day group. Because this finding was noted for a single fetus and the mean litter proportion (0.3% per litter) was within the
WIL Research historical control data range (0.0% to 0.7% per litter) and was not statistically significantly different from the concurrent control group, it was not considered test substance-related. Fetus no. 14005-06 in the 100 mg/kg/day group had situs inversus (lateral transposition of the trachea, esophagus, heart, great and major vessels, lungs, liver, stomach, pancreas, spleen, kidneys, adrenals, and intestine). Because this finding was observed in a single fetus and was not noted in the higher dosage levels, it was not considered test substance-related. In the control group, fetus no.
13989-07 had a malpositioned kidney (left). No test substance-related soft tissue developmental variations were noted for fetuses in the 100, 300, and 1000 mg/kg/day groups. An increased mean litter proportion of renal papilla(e) not developed and/or distended ureter(s) was noted in the 1000 mg/kg/day group (6.9% per litter) compared to the control group (1.3% per litter). Although the difference from the concurrent control group was not statistically significant, the value exceeded the maximum mean value in the WIL Research historical control data (4.0% per litter). However, this is the most common soft tissue developmental variation in the WIL Research historical control database and the majority (13 of 25 occurrences) of this finding was noted in fetuses from a single litter (no. 14023). Therefore, this soft tissue developmental variation was not attributed to maternal test substance administration. Other soft tissue developmental variations, including pale spleen, accessory lobule(s) of the liver, and major blood vessel variation (right subclavian artery coursed retroesophageal and joined aortic arch adjacent to ductus arteriosis [no brachiocephalic trunk]), were noted infrequently, at similar frequencies in the concurrent control group, and in a manner that was not dose-related. One, 3, and 2 fetuses in the control, 100, and 1000 mg/kg/day groups, respectively, were noted with renal papilla(e) not fully developed (Woo and Hoar Grade 1). This finding was not classified as either a malformation or developmental variation, was not included on the summary tables, and was not considered to be test substance-related because it occurred in a manner that was not dose-related.

SKELETAL MALFORMATIONS AND VARIATIONS
There were no test substance-related skeletal malformations noted for fetuses at any dosage level. Fetus no. 14004-05 in the 300 mg/kg/day group was noted with a costal cartilage anomaly (fused costal cartilages) and fetus no. 14071-16 in the 100 mg/kg/day group had a skull anomaly (a 1 mm opening in the right parietal bone). Because these malformations were noted in single fetuses, in a non-dose-related manner, and the mean litter proportions were not statistically significantly different from the control group, the findings were not considered test substance-related. No skeletal malformations were noted in the 1000 mg/kg/day group. In the control group, fetus no. 14015-02 had a rib anomaly (extra and forked rib).
No test substance-related skeletal developmental variations were noted for fetuses in the 100, 300, and 1000 mg/kg/day groups. A significantly (p<0.05) lower mean litter proportion of cervical centrum no. 1 ossified was noted for fetuses in the 1000 mg/kg/day group (8.4% per litter) compared to the concurrent control group (26.1% per litter). However, this is the most common skeletal developmental variation in the WIL Research historical control database and the value was within the WIL Research historical control data range (1.4% to 35.8% per litter); therefore, in the absence of any other signals of developmental toxicity or effects on fetal weight, this finding was not attributed to maternal test substance administration. Other skeletal developmental variations observed in the test substance-treated groups were noted in single fetuses, occurred infrequently, did not occur in a dose-related manner, and/or the mean litter proportions were within the WIL Research historical control data ranges. Therefore, these findings were not
considered test substance-related.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no changes

Remarks on result:

not determinable

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Based on reduced mean food consumption values with corresponding decreases in mean body weight gains at 1000 mg/kg/day during the first week of treatment, a dosage level of 300 mg/kg/day was considered to be the no-observed-adverse-effect level (NOAEL) for maternal toxicity. Intrauterine growth, survival, and external, visceral, and skeletal fetal morphology were unaffected by test substance administration at all dosage levels. Based
on these results, a dosage level of 1000 mg/kg/day (the highest dosage level tested) was considered to be the no-observed-adverse-effect level (NOAEL) for embryo/fetal developmental toxicity when Texanol™ was administered orally by gavage to bred Crl:CD(SD) rats.

Executive summary:

The test substance, Texanol™, was administered orally by gavage to 3 groups of 25 bred female Crl:CD(SD) rats once daily from gestation days 1 through 19. Dosage levels were 100, 300, and 1000 mg/kg/day administered at dosage volumes of 0.11, 0.32, and 1.05 mL/kg, respectively. A concurrent control group composed of 25 bred females received the vehicle (deionized water) on a comparable regimen at a dosage volume of 1.05 mL/kg. The females were approximately 13 weeks of age at the initiation of dose administration. All animals were observed twice daily for mortality and moribundity. Clinical observations, body weights, and food consumption were recorded daily. On gestation day 20, a laparohysterectomy was performed on each female. The uteri, placentae, and ovaries were examined, and the numbers of fetuses, early and late resorptions, total implantations, and corpora lutea were recorded. Gravid uterine weights were recorded, and net body weights and net body weight changes were calculated. The fetuses were weighed, sexed, and examined for external, visceral, and skeletal malformations and developmental variations.

All females survived to the scheduled necropsy on gestation day 20. Test substance-related increased incidences of red and/or clear material around the mouth were noted for females in the 100, 300, and 1000 mg/kg/day groups approximately 1 hour following dose administration. In addition, low incidences of red material around the nose and yellow material around the urogenital area were noted for females in the 100, 300, and/or 1000 mg/kg/day groups at the daily examinations and/or approximately 1 hour following dose administration. However, the post-dose findings did not generally persist to the daily examinations the following day, and in the absence of other signs of systemic toxicity at these dosage levels, these clinical findings were considered non-adverse. Test substance-related reductions in mean food consumption values with corresponding decreases in mean body weight gains were noted in the 1000 mg/kg/day group during gestation days 1-3 and 3-6 compared to the control group. Mean body weight gains and food consumption in this group were similar to the control group during the remainder of the dosing period (gestation days 6-20). The initial lower mean body weight gains in this group resulted in a lower mean body weight gain when the overall dosing period (gestation days 1-20) was evaluated compared to the control group; however, this change occurred in the absence of reduced food consumption. Mean net body weight gain in this group was also lower than the control group, while mean net body weight and gravid uterine weight were similar to the control group. The test substance-related changes in mean body weight gain and food consumption at 1000 mg/kg/day during gestation days 1-6 were considered adverse. There were no test substance-related effects on mean maternal body weights, body weight gains, food consumption, net body weights, net body weight gains, and gravid uterine weights at 100 and 300 mg/kg/day. No test substance-related macroscopic findings were noted at any dosage level. Intrauterine growth and survival were unaffected by test substance administration at 100, 300, and 1000 mg/kg/day. In addition, there were no test substance-related external, visceral, or skeletal fetal malformations or developmental variations observed at any dosage level.

Based on reduced mean food consumption values with corresponding decreases in mean body weight gains at 1000 mg/kg/day during the first week of treatment, a dosage level of 300 mg/kg/day was considered to be the no-observed-adverse-effect level (NOAEL) for maternal toxicity. Intrauterine growth, survival, and external, visceral, and skeletal fetal morphology were unaffected by test substance administration at all dosage levels. Based on these results, a dosage level of 1000 mg/kg/day (the highest dosage level tested) was considered to be the no-observed-adverse-effect level (NOAEL) for embryo/fetal developmental toxicity when Texanol™ was administered orally by gavage to bred Crl:CD(SD) rats.