Methyl carbamate

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From February 17, 1987 to March 12, 1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to method equivalent to OECD Guideline 414, in compliance with GLP.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1988

Report date:

1988

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Methyl carbamate

EC Number:

209-939-2

EC Name:

Methyl carbamate

Cas Number:

598-55-0

Molecular formula:

C2H5NO2

IUPAC Name:

methyl carbamate

Test material form:

other: Crystalline solid

Test animals

Species:

rat

Strain:

other: Sprague Dawley Crl:CD BR

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River breeding laboratories, Inc., Portage, Michigan
- Age at study initiation: 71 d
- Housing: All animals were individually housed in clean, wire-mesh cages suspended above cage-board
- Diet: Purina® Certified Rodent Chow.
- Water: ad libitum
- Acclimation period: 19 d

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22±16°C (72±3°F)
- Humidity (%): Minimum relative density - 40%
- Air changes: 10 fresh air changes per h
- Photoperiod: 12 h light and 12 h dark photoperiod

IN-LIFE DATES: From February 17, 1987 to March 12, 1987

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: deionized water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The appropriate amount of test substance (not adjusted for purity) was weighed for each group. The test substance was transferred to a volumetric flask via a series of vehicle rinses. The flasks were brought to volume with deionized water, inverted and shaken several times. The mixture was stirred for 10 min utilizing a magnetic stir plate and bars, then transferred to a dosing bottle for administration. The dosing solutions were prepared and dispensed daily. Dosing samples, 10 mL each, were collected daily from each group.

Details on mating procedure:

- Impregnation procedure: cohoused
- Proof of pregnancy: Presence of a copulatory plug referred to as Day 0 of pregnancy

Duration of treatment / exposure:

Day 6 to Day 15 of gestation

Frequency of treatment:

Once daily

Duration of test:

39 d (approximately)

No. of animals per sex per dose:

25 pregnant females per group

Control animals:

yes, concurrent vehicle

Examinations

Maternal examinations:

CLINICAL OBSERVATIONS AND SURVIVAL: Yes
- Time schedule: All rats were examined daily for appearance and behavior prior to dosing, and for any clinical signs of toxicity, moribundity and mortality following dosing

BODY WEIGHT: Yes
- Time schedule for examinations: Maternal body weights for all females were recorded on gestation Day 0, 6, 9, 12, 16 and 20. Mean body weight changes were calculated for each corresponding interval and for Day 6-16 and 0-20.

POST-MORTEM EXAMINATIONS: Yes
- Each female was sacrificed by carbon dioxide asphyxiation on gestation Day 20
- Organs examined: Uterus and ovary

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
OTHERS
- Number and location of viable and nonviable fetuses was recorded.
- Maternal tissues were retained for possible microscopic examination only as deemed necessary by macroscopic necropsy findings.
- Uteri with no evidence of macroscopic implantation were excised, opened and placed in 10% ammonium sulfide solution for detection of early implantation
loss.

Fetal examinations:

- External examinations: Yes (all per litter) Examination of the eyes, palate, and external orifices.
- Soft tissue examinations: Yes (half of fetuses)
- Skeletal examinations: Yes(half of fetuses)
- Head examinations: No data

OTHERS:
- The crown-rump lengths of late resorptions were recorded and the tissues were discarded.
- Fetal kidneys were examined and graded for renal papillae development.
- External, visceral and skeletal findings were recorded as developmental variations or malformations

Statistics:

All analyses were conducted using two-tailed tests for a minimum significance level of 1% and 5% comparing the treatment group to the control group. All group means are presented with standard deviations. The numbers of animals (N) used to calculate the means are provided on the individual data tables. All statistical tests were performed by a digital computer with appropriate programming as referenced below:
1. The fetal sex ratios were compared by the Chi-square test with Yates' correction factor.
2. The numbers of litters with malformations and variations were compared by Fisher's Exact Test
3. The numbers of early and late resorptions, dead fetuses and postimplantation losses were compared by the Mann-Whitney U-test.
4. Mean numbers of corpora lutea, total implantations, viable fetuses, mean fetal body weights, maternal body weights at each interval and maternal body weight gains were analyzed by a one-way analysis of variance, and Dunnett's test

Historical control data:

Yes

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
CLINICAL OBSERVATIONS AND SURVIVAL
All animals survived to the scheduled gestation Day 20 sacrifice. Minimal clinical signs observed at the 300 mg/kg bw/day were decreased defecation, soft stool, mucoid feces and anogenital or vaginal staining of the fur. Only a limited number of animals were affected. None of these findings were severe or persistent.
No significant clinical signs of a treatment-related effect were observed at any other dose levels.

BODY WEIGHTS
Mean body weight gain was decreased during the initial 6 d of test substance administration only at the 300 mg/kg bw/day dose level. The lower body weight gains in the 300 mg/kg bw/day group for gestation days 6-9 and 9-12 were statistically significant when compared to the respective control values. The
decreased gain during the initial treatment period resulted in a decreased maternal body weight gain over the entire treatment interval (gestation Day 6-
16). During the last 4 d of the treatment period (gestation Day 12-16) and following the treatment period (gestation Day 16-20), the body weight gains in
the 300 mg/kg bw/day dose group were comparable to the corresponding control values. However, the mean body weights at this dose level were statistically
decreased when compared to the respective control values on gestation Day 12, 16 and 20. Mean body weight gain was slightly decreased at all intervals evaluated throughout the treatment period in the 150 mg/kg bw/day dose group when compared to the control group but the differences were not statistically
significant. No substance-related effect was apparent on the body weight data in the 30 mg/kg bw/day dose group. All of the mean body weight and mean body weight change values were comparable to the respective control values.

NECROPSY DATA
None of the necropsy findings observed at the scheduled sacrifice were indicative of a substance-related effect. Two abnormal spleen findings were recorded, one in the 30 mg/kg bw/day dose group (a white, firm area on the spleen) and one in the 150 mg/kg/day dose group (a rough spleen with firm, white areas).
The only other necropsy finding was dilated renal pelvis. The incidence of this finding in the 0, 30, 150 and 300 mg/kg bw/day dose groups was as follows: 1,0, 0 and 2, respectively.

Effect levels (maternal animals)

Dose descriptor:

NOEL

Effect level:

30 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
GESTATION DAY 20 CESAREAN SECTION DATA
The fetal body weight values were statistically decreased (p < 0.01) in the 150 and 300 mg/kg bw/day dose groups when compared to the control value. The fetal body weight value at the lowest dose level (30 mg/kg bw/day) was comparable to that in the control group. Intrauterine survival was not apparently affected by the administration of test substance at any dose level. The mean numbers of viable fetuses, early and late resorptions, corpora lutea and implantation sites at all dose levels were not different from their respective control values. The fetal sex distribution in the test substance treated groups were also similar to that in the control group. None of these values were statistically different from the control group values.

FETAL MORPHOLOGICAL DATA
The spontaneous occurrence of fetal malformations in this study was not indicative of a teratogenic response. Malformations were observed in 2, 1 and 2 fetuses in the 30, 150 and 300 mg/kg bw/day treated groups. At 30 mg/kg bw/day, one fetus had microphthalmia and a fetus from another litter had vertebral and rib anomalies. One fetus in 150 mg/kg bw/day dose group had thread-like tail. The two fetuses with malformations in the 300 mg/kg bw/day dose group were from separate litters. One had an umbilical hernia and the other had hydrocephaly. Although there were no fetal anomalies observed in the concurrent control group in this study, all of the malformations seen in this study also appear in historical control data. The numbers of litters with fetuses having malformations were not statistically significant when compared to the control group.

The percentage of fetuses (and litters) with 25 presacral vertebrae and bent ribs was slightly increased in the 150 and 300 mg/kg bw/day groups in comparison with the control group. The number of litters at the 150 and 300 mg/kg bw/day dose levels with these variations was not statistically significant. In addition, the values were either comparable to or within the range of the historical data of this laboratory. The incidence and types of the remaining fetal developmental variations in the test substance treated groups were not remarkable when compared to those in the vehicle control group.

Effect levels (fetuses)

Dose descriptor:

NOEL

Effect level:

30 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: fetotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The NOEL for maternal toxicity and fetotoxicity was considered to be 30 mg/kg bw/day.

Executive summary:

A study was conducted to assess the potential of test substance to induce maternal, embryotoxic and teratogenic effects after maternal exposure from implantation to one day prior to expected parturition, by method comparable to OECD guideline 414, in compliance with GLP. The test substance was administered to 4 groups of 25 bred female Crl:CD BR rats by oral gavage at a dose level of 0 (vehicle: deionized water), 30, 150, and 300 mg/kg bw/day once daily from gestation Day 6 through 15. Animals were observed daily for appearance and behavior prior to dosing, and for any clinical signs of toxicity, moribundity and mortality following dosing. Body weights were recorded on Day 0, 6, 9, 12, 16 and 20 of gestation. All females were sacrificed on Day 20 by carbon dioxide asphyxiation and the contents were examined. Uterus and ovaries were examined. The numbers of fetuses, early and late resorptions, total implantations, and corpora lutea were recorded. The fetuses were weighed, sexed, and examined for external, visceral, and skeletal malformations. No death occurred during the study. Minimal clinical signs such as decreased defecation, soft stool, mucoid feces and anogenital or vaginal staining of the fur were observed only in limited number of animals at 300 mg/kg bw/day dose level. Statistically significant decrease in mean body weight gain was noted in 300 mg/kg bw/day dose group. No treatment related effect was observed in necropsy findings. Fetal body weights were also decreased in 150 and 300 mg/kg bw/day dose groups. There was no substance related effect on the mean numbers of viable fetuses, early and late resorptions, corpora lutea , implantation sites and fetal sex distribution at all dose levels were not different from their respective control. Some spontaneous fetal malformations occur in this study. However these were within the range of historical control data and was not indicative of a teratogenic response. Under the study conditions, the NOEL for maternal toxicity and fetotoxicity was considered to be 30 mg/kg bw/day (Nemec MD, 1988).