ε-caprolactam

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1980

Report date:

1980

Reference 2

Reference Type:

publication

Title:

Developmental Toxicity Studies of Caprolactam in the Rat and Rabbit.

Author:

Gad S.C. et al.

Year:

1987

Bibliographic source:

J. Appl. Toxicol. 7, 317-326

Reference 3

Reference Type:

publication

Title:

Rat and rabbit teratology studies of Caprolactam.

Author:

Gad, S.C. et al.

Year:

1984

Bibliographic source:

Proc. Symp. Ind. Approach Chem. Risk Assess. Caprolactam Relat. Compd. Case Study, 164-189.

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

Older study reports

Principles of method if other than guideline:

This study was designed to evaluate the developmental toxicity potential of the test substance in rats.
The test material was administered by oral intubation on days 6 through 15 of gestation to each of three groups of twenty pregnant female rats of the Fischer 344 strain at levels of 100, 500, and 1000 mg/kg bw, respectively. A fourth group of twenty pregnant rats received only the vehicle (distilled water) and served as the control group. Criteria evaluated for evidence of compound effect were maternal body weight and body weight changes, food consumption, clinical observations, survival, gross pathology, implantation and resorption efficiencies, and offspring viability and development.

GLP compliance:

yes

Remarks:

(Hazleton Laboratories America, Inc.)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

ε-caprolactam

EC Number:

203-313-2

EC Name:

ε-caprolactam

Cas Number:

105-60-2

Molecular formula:

C6H11NO

IUPAC Name:

azepan-2-one

Specific details on test material used for the study:

- Name of test material (as cited in study report): Caprolactam
- Physical state: white crystalline solid
- Analytical purity: approximately 100 %

Test animals

Species:

rat

Strain:

Fischer 344

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Microbiological Associates, Walkerville, Maryland
- Weight at study initiation: 149-205 g
- Diet (e.g. ad libitum): Purina Laboratory Chow
- Water (e.g. ad libitum): Tap water
- Acclimation period: 20 days

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Appropriate amounts of the test material were dissolved in distilled water on a weight-per-volume basis and administered by oral intubation (amount based on individual body weight, dosing factor 10 ml/kg bw) from day 6 through day 15 of gestation.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/2
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

day 6-15 of gestation

Frequency of treatment:

daily

Duration of test:

day 20 of gestation

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

100 mg/kg bw/day

Doses / concentrations 3

Dose / conc.:

500 mg/kg bw/day

Doses / concentrations 4

Dose / conc.:

1 000 mg/kg bw/day

No. of animals per sex per dose:

20

Control animals:

yes, concurrent no treatment

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: during day 6-20 of gestation


BODY WEIGHT: Yes
- Time schedule for examinations: on days 0, 6, 11, 15, and 20 of gestation


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption for each animal determined: Yes on days 6, 11, 15, and 20 of gestation


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined:

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes

Fetal examinations:

- External examinations: Yes
- Soft tissue examinations: Yes
- Skeletal examinations: Yes

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Clinical observations made during the treatment and post treatment periods that were noted in the treated groups: urine stains, a rough hair coat, a red discharge from the vagina, a bloody crust on or about the eyes, mouth, and/or nose, a thin and/or hunched appearance, and/or depression.

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, treatment-related

Description (incidence):

The maternal survival rate was statistically significantly lower in the high-dose group when compared with the control. Nine high-dose females (six pregnant, three not pregnant) were found dead during the treatment phase of this study.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The mean body weight values of the high dose group on day 15 and 20 of gestation and the mean body weight changes of the mid- and high dose groups for the days 6-11 and 6-15 were statistically significantly (p<0.05) lower than the control values at these intervals (Table 1). The percent body weight change in the mid dose group during the treatment period 6-11 and 6-15 were -0.8 and 5.2, respectively, in comparison to 6.2 and 13.4 in control group. Similarly in the high dose group, the percent body weight change were -2.7 and 2.3, respectively.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

The mean food consumption was significantly lower (p<0.05) in the mid- and high-dose groups.

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

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

effects observed, treatment-related

Description (incidence and severity):

The pregnancy rates were slightly higher in the low- and mid-dose groups (80 and 75%) than in the control (60%). The mean implantation efficiencies were slightly lower in the low-and high-dose groups than in the control (Table 2). The mean incidence of resorptions was statistically significantly (p<0.05) higher than the control value in the high-dose group (Table 2).

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

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

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

The mean body weight of the male fetuses in the treated groups was slightly lower than that of the control group, and the mean body weight of the female fetuses in the mid-and high-dose groups was slightly lower than that of the control group. The difference in the mean body weight was remarkable only in the high dose males (10% low) and females (15% low), however the difference was not statistically significant.

Reduction in number of live offspring:

effects observed, treatment-related

Description (incidence and severity):

The mean incidence of fetal death was comparable for all groups, and the mean incidence of fetal viability was lower in the high-dose group than in the control group.

Changes in sex ratio:

not examined

Changes in litter size and weights:

not examined

Changes in postnatal survival:

not examined

External malformations:

not examined

Skeletal malformations:

no effects observed

Description (incidence and severity):

No treatment-related visceral or skeletal anomalies were observed. Skeletal variants were observed in each group with the mid- and high dose groups having a higher incidence of skeletal variants than the control group. In the control group the variants included incomplete ossification of the skull (supraoccipital or interparietal), a nonfused vertebral column (centra), and/or extra ribs. The variants observed in the treated groups included incomplete ossification of the skull (supraoccipital and/or interparietal), incomplete and/or malfused sternebrae, extra ribs, and/or nonfused and/or incomplete ossification of the vertebral column (centra). No statistically significant differences were noted in these data.

Visceral malformations:

no effects observed

Description (incidence and severity):

No treatment-related visceral or skeletal anomalies were observed. Skeletal variants were observed in each group with the mid- and high dose groups having a higher incidence of skeletal variants than the control group. In the control group the variants included incomplete ossification of the skull (supraoccipital or interparietal), a nonfused vertebral column (centra), and/or extra ribs. The variants observed in the treated groups included incomplete ossification of the skull (supraoccipital and/or interparietal), incomplete and/or malfused sternebrae, extra ribs, and/or nonfused and/or incomplete ossification of the vertebral column (centra). No statistically significant differences were noted in these data.

Other effects:

effects observed, treatment-related

Description (incidence and severity):

The mean fetal lengths were slightly lower (below 10 %) in the high dose-group than in the controls.

Effect levels (fetuses)

1

Dose descriptor:

NOAEL

Effect level:

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

Basis for effect level:

other: fetotoxicity

2

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (actual dose received)

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Table 1. Mean maternal body weights and body weight changes^a

Body weights	Days	Dose level (mg/kg bw)
		0	100	500	1000
Mean weight (g)	0	167.2	174.4	170.8	168.0
	6	176.7	184.4	180.7	176.8
	11	187.6	192.9	179.3	172.0
	15	200.3	204.4	190.1	180.8^s-
	20	234.6	233.9	225.3	208.8^s-
Mean change (g)
Pre-treatment period	0-6	9.5	10.5	9.9	8.8
Treatment period	6-11	10.9	8.0	-1.4^s-	-4.8^s-
Treatment period	11-15	12.7	11.5	10.8	8.8
Total Treatment period	6-15	23.6	19.5	9.4^s-	4.0^s-
Post-treatment period	15-20	34.3	29.5	35.2	28.0
Total study period	0-20	67.4	59.5	54.5	40.8
Percent change (%)
Pre-treatment period	0-6	5.7	6.0	5.8	5.2
Treatment period	6-11	6.2	4.3	-0.8	-2.7
Treatment period	11-15	6.8	6.0	6.0	5.1
Total Treatment period	6-15	13.4	10.5	5.2	2.3
Post-treatment period	15-20	17.1	14.4	18.5	15.5
Total study period	0-20	40.3	34.1	31.9	24.3

^aOnly data from pregnant rats surviving to Day 20 of gestation were included in calculations of the mean values

S-:Statistically significantly (p<0.05) lower than the control value.

Table 2. Summary of the Ovarian, Uterine, and Litter Data^a

Parameters	Dose level (mg/kg bw)
	0	100	500	1000
Number of females mated	20	20	20	20
Number of rats pregnant	12	16	15	11
Pregnancy rate (%)	30.0	80.0	75.0	55.0
Number of pregnant rats surving to day 20	12	16	15	5
Maternal survival rate (%)	100.0	100.0	100.0	45.5
Mean number of:
Corpora lutea	11.8	12.9	11.7	12.8
Implantations	9.6	8.5	9.6	8.6
Resorptions	0.4	0.5	0.3	3.2
Fetuses- Dead	0.0	0.0	0.0	0.0
Fetuses- Live	9.2	8.6	9.3	5.4
Indices calculated on aper litter per group basis:
Mean implantation efficiency (%)	81.78	70.56	81.11	67.92
Mean incidence of resorption (efficiency) (%)	4.64	5.24	3.27	41.34
Mean incidence of fetal death (%)	0.00	0.00	0.00	0.00
Mean incidence of fetal viability (%)	95.36	94.76	96.39	58.66

^aOnly data from pregnant rats surviving to Day 20 of gestation were included in calculations of the mean values

S-:Statistically significantly (p<0.05) lower than the control value.

S+:Statistically significantly (p<0.05) higher than the control value.

Applicant's summary and conclusion

Conclusions:

The NOAEL for the maternal rats has been found to be 100 mg/kg bw/day due to body weight gain. The NOAEL for the fetuses has been found to be 500 mg/kg bw/day for fetotoxicity (mean fetal body weight and viability) and 1000 mg/kg bw/day for teratogenicity (the highest dose tested).

Executive summary:

This study was designed to evaluate the developmental toxicity potential of the test substance in rats. The test material was administered by oral intubation on days 6 through 15 of gestation to each of three groups of twenty pregnant female rats of the Fischer 344 strain at levels of 100, 500, and 1000 mg/kg bw, respectively. A fourth group of twenty pregnant rats received only the vehicle (distilled water) and served as the control group. Criteria evaluated for evidence of compound effect were maternal body weight and body weight changes, food consumption, clinical observations, survival, gross pathology, implantation and resorption efficiencies, and offspring viability and development. The NOAEL for the maternal rats has been found to be 100 mg/kg bw/day due to body weight gain. The NOAEL for the fetuses has been found to be 500 mg/kg bw/day for fetotoxicity (mean fetal body weight and viability) and 1000 mg/kg bw/day for teratogenicity (the highest dose tested).