Methacrylonitrile

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

no data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Peer reviewed literature data

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1996

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: no data

Deviations:

not specified

Principles of method if other than guideline:

Timed-pregnant Spague Dawley outbred rats were dosed by gavage with methacrylonitrile in distilled water during major organogenesis

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Methacrylonitrile

EC Number:

204-817-5

EC Name:

Methacrylonitrile

Cas Number:

126-98-7

Molecular formula:

C4H5N

IUPAC Name:

2-methylprop-2-enenitrile

Details on test material:

- Purity: 96 %

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 207-275 g on GD zero (the day of vaginal sperm detection).
- Fasting period before study:
- Housing: Females were housed singly in solid bottom polyvcarbonate cages with stainless steel lids and Ad-Sorb-Dri litter
- Diet: ad libitum
- Water: deionised/filtered water ad libitum
- Acclimation period: 7 day quarantine period

ENVIRONMENTAL CONDITIONS
- Temperature: 72 degrees Fahrenheit (average)
- Humidity: 55 % (average)
- Air changes: 10-14 times per hour (estimated)
- Photoperiod: 12 h light and 12 h dark

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: deionised water

Details on exposure:

PRELIMINARY STUDY

Test material at doses of zero, 10, 50, 75, 100 or 125 mg/kg/day were administered by gavage to pregnant rats on gestational days 6-15.

MAIN STUDY

Test material at doses of zero, 5, 25 or 50 mg/kg/day were administered by gavage to pregnant rats on gestational days 6-15. The dose volume (5 mL/kg) was based on bodyweight during the study.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Dosing solutions were verified to be within ± 10 % of the theoretical concentration by gas chromatography prior to administration. Each dosing solution was coded so that treatment and examination of animals was performed without knowledge of the dose levels.

Details on mating procedure:

Animals were individually identified by tail tattoo during a 7 day quarantine. After quarantine, individual females were placed overnight in the home cage of a singly housed male of the same stock for mating and then examined the next morning for the presence of vaginal sperm.

Duration of treatment / exposure:

Days 6 to 15 of gestation

Frequency of treatment:

Daily

Duration of test:

Days zero to 20 of gestation

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 5, 25, 50 mg/kg/day
Basis:
actual ingested

No. of animals per sex per dose:

Twenty six

Control animals:

yes, concurrent vehicle

Details on study design:

The study was conducted using a two-replicate design with 13 animals per group or replicate. Mated females were randomly assigned to dose groups using a randomisation procedure stratified by bodyweight on GD zero, so that body weights were not significantly different.

Examinations

Maternal examinations:

Animals were weighed on GD zero and daily during treatment. Food and water consumption was measured at 2 to 3 day intervals throughout the study, beginning on GD zero. Clinical signs were recorded at least once per day during the treatment periods.

Ovaries and uterine content:

Following termination by carbon dioxide asphyxiation on GD 20, maternal liver weight and gravid uterine weight were measured. Uterine contents were evaluated for the number of implantation sites, resorptions, late fetal deaths (fetuses with discernible digits and weighing greater than 0.8 g) but displaying no vital signs at the time of uterine dissection), and live fetuses. The uterus was stained to reveal possible early resorptions when evidence of pregnancy was not apparant.

Fetal examinations:

Live fetuses were dissected from the uterus and anaethetised by inducing hypothermia. Each live fetus was weighed and examined for external morphological abnormalities; the viscera were then examined using a fresh tissue dissection technique. Half of the fetuses were decapitated prior to dissection and the heads were fixed in Bouin's solution for free-hand sectioning and examination. All fetal carcasses were cleared and stained with Alcian blue/Alizarin red S and examined for fetal malformations.

Statistics:

Analyses of data were carried out using the General Linear Model (GLM) procedures in the SAS software library. Prior to analysis, an arcsine square root transformation was performed on all litter-derived percentage data. Dose response relationships for selected measures were evaluated with the test for linear trend. Analysis of variance (ANOVA) was used to determine whether significant dose effects, replicate effects, or dose x replicate interactions had occurred. Absence of a significant dose x replicate interaction indicated that the pooling of replicate data was valid. When ANOVA revealed a significant main effect for dose, Williams' multiple comparison test and Dunnett's test were used to compare each treated group to the concurrent control group (α = 0.05). Nominal scale measures were analysed by a test for linear trend on proportions and a chi-square test for independence among treatment groups. When the chi-square test for independence revealed significant (p = < 0.05) differences among groups, then a Fisher one-tailed exact probability test (α = 0.05) was used for pairwise comparisons between each treated group and the concurrent control group.

Indices:

No data

Historical control data:

No data

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
PRELIMINARY STUDY

Signs of systemic toxicity, including rough coat, lethargy and hunched posture were noted in all animals at ≥ 50 mg/kg/day with increased severity in a dose related manner. No clinical signs of toxicity were noted at 10 mg/kg/day. Mortality or morbidity was observed in 11 % (1/9), 50 % (4/8) and 60 % (6/10) of the animals in the 75, 100 and 125 mg/kg/day groups, respectively. Maternal bodyweight was significantly decreased at ≥ 50 mg/kg/day compared to controls. In addition, maternal bodyweight gain during gestation was decreased in all test material groups, while maternal weight gain during treatment and corrected maternal weight gain were decreased at ≥ 50 mg/kg/day compared to controls.

MAIN STUDY

Full results are presented in Table 1 (attached).

No maternal deaths, morbidity or distinctive clinical signs were observed and there were no significant adverse effects on maternal body weight or weight change during or after exposure to the test material. No persistent adverse effect on maternal food and water consumption was recorded. Necropsy of maternal animals on GD 20 revealed no effect of treatment on gravid uterine weight but maternal liver weight (absolute, relative and adjusted) was increased at the mid and high dose levels. Examination of the uteri demonstrated that 96-100 % of the mated animals in the control and high dose treatment group were pregnant.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

> 50 mg/kg bw/day

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
PRELIMINARY STUDY
Totally resorbed litters were observed in 10 % (1/10). 25 % (1/4) and 50 % (2/4) of the pregnant animals in the 10, 100 and 125 mg/kg/day groups, respectively, but not in other groups. There was no effect on fetal body weight at any dose. Morphological development was not evaluated.

MAIN STUDY

All pregnant animals in the zero, 5, 25 and 50 mg/kg/day dose groups had one or more live fetuses on GD 20 (see Table 2, attached). There were no differences between the treated groups and the control group in the average number of implantation sites per litter, postimplantation deaths per litter, live fetuses per litter, or mean fetal weight per litter (see Table 2, attached). When fetal weight per litter was examined separately by sex, no treatment related differences were observed (data not shown). There was no effect of treatment on the incidence of morphological abnormalities (see Tables 2 and 3, attached).

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

> 50 mg/kg bw/day

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

At doses up to 50 mg/kg/day there was no effect on postimplantation survival, fetal weight or morphological development in rats. Hence, in the absence of any indication of maternal toxicity, the NOAEL for maternal toxicity is ≥ 50 mg/kg/day. The NOAEL for development toxicity in the rat is also ≥ 50 mg/kg/day.