Aziridine

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

August - November 1973

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study, well documented and acceptable for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1975

Report date:

1975

Materials and methods

Principles of method if other than guideline:

The study was conducted according to FDA Guidelines: "Guidelines for reproduction studies for safety evaluation of drugs for human use", Food and Drug Administration, Washington, January 1966.

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Ethylenimine

IUPAC Name:

Ethylenimine

Details on test material:

- Name of test material (as cited in study report): Aethylenimin
- Physical state: liquid
- Analytical purity: 100 % (stabilised by NaOH)

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: WIGA, Sulzfeld
- Age at study initiation: no data
- Weight at study initiation: no data
- Housing: 2 animals/cage
- Diet (ad libitum): Altromin-R (Altrogge, Lage/Lippe)
- Water: ad libitum


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2
- Humidity (%): 55 ± 5
- Photoperiod (hrs dark / hrs light): 12 h / 12 h

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

VEHICLE
- pH: 7.0
- Amount of vehicle (if gavage): 500 µL/100 g animal

Analytical verification of doses or concentrations:

no

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: no data
- Length of cohabitation: 12 hours
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

Day 6 to 15 of pregnancy

Frequency of treatment:

daily

Duration of test:

20 days

Doses / concentrations

Remarks:

Doses / Concentrations:
3.1 and 1.24 µL/kg bw (corresponding to approx. 2.57 and 1.03 mg/kg bw) (Recalculation based on relative density at 24 °C = 0.83)
Basis:
actual ingested

No. of animals per sex per dose:

Dose group 1 (2.57 mg/kg bw): 34 females;
Dose group 2 (1.03 mg/kg bw): 23 females;
Control group 1 (untreated): 26 females;
Control group 2 (untreated): 17 females

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: based on acute oral gavage toxicity study

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily


BODY WEIGHT: Yes
- Time schedule for examinations: 3 times/week


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: gross-pathologically (organs not specified)

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of medium late resorptions: Yes
- Number of late resorptions: Yes
- Placenta weight: Yes

Fetal examinations:

- Fetal body length and weight: Yes: all per litter
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: 1/3 per litter
- Skeletal examinations: Yes: 2/3 per litter
- Head examinations: No

Statistics:

Analysis of variance, t-test, and Chi-square-test (* >= 95 %, ** >= 99 %, compared to the untreated control)

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:yes

Details on maternal toxic effects:
Several rats of the high dose group showed vaginal bleeding. 2 aborts occurred. Body weights were reduced in this test group as compared to the control. The animals of the low dose group remained without clinical signs of toxicity. No mortality occurred after oral administration of the test substance. In the untreated control groups no clinical signs of toxicity and lethality were observed.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

ca. 1.03 mg/kg bw/day (actual dose received)

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
At the high dose level the percentage of living fetuses based on the number of implantations was decreased, and the number of dead implantations increased compared to the untreated control. Mean weight and length of the fetuses was reduced in the high dose group. The incidence of skeletal and organ malformations and retardations and variations was significantly increased compared to the control.
In the low dose group no embryolethal, fetotoxic or teratogenic effects were observed. The only effects noted were decrease of the mean length of the fetuses and of the mean placental weight.

Effect levels (fetuses)

1

Dose descriptor:

NOAEL

Effect level:

ca. 1.03 mg/kg bw/day (actual dose received)

Basis for effect level:

other: teratogenicity

2

Dose descriptor:

NOAEL

Effect level:

ca. 1.03 mg/kg bw/day (actual dose received)

Basis for effect level:

other: fetotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Clinical symptoms:

In the group treated with 3.1 µL/kg bw of the substance 6 rats showed vaginal bleedings on day 14, 2 rats on day 15, 3 rats on day 14 and 15 and 1 rat on day 15 and 18 post coitum. 2 rats of this group had an abort.

The rats treated with 1.25 µL/kg bw of the substance as well as the control group showed no clinical symptoms.

 

 

Mortality:

There were no substance-related or spontaneous mortalities in any of the test groups.

 

 

Body weight:

Rats treated with 3.1 µL/kg bw of the test substance showed a decrease in body weight. 1.24 µL/kg bw had no effect.

 

 

Conception rate:

The rate of conceptions and implantations were not changed in animals treated with the test substance compared to the control groups.

 

 

Living fetuses:

The percentage of living fetuses based on the number of implantations was decreased in the dose group treated with 3.1 µL/kg bw of the test substance (40.24%) compared to the corresponding control group (96.61%). No significant change was observed in the dose group treated with 1.24 µL/kg bw (88.1%) compared to the corresponding control group (93.44%).

 

 

Dead implantations:

The number of dead implantations was significantly increased after application of 3.1 µL/kg bw of the test substance compared to the control. After application of 1.24 µL/kg bw of the test substance the number of dead implantations corresponds to the number in control animals.

 

 

Weight and length of the fetuses and weight of the placenta:

The mean weight of the fetuses was significantly reduced after application of 3.1 µL/kg bw of the test substance. Application of 1.24 µL/kg bw of the test substance had no effect.

The mean length of the fetuses was significantly reduced after application of 1.24 or 3.1 µL/kg bw of the test substance.

The mean placental weight was significantly reduced after application of 1.24 or 3.1 µL/kg bw of the test substance.

 

 

External examination of the fetuses:

1 fetus of the dosis group 1.24 µL/kg bw showed ectopia visceralis. In none of the other groups changes of the fetuses were observed.

 

 

Skeletal and organ examination:

After application of 3.1 µL/kg bw of the test substance 18 fetuses showed malformations. The number was significantly increased compared to the untreated control group. Most of the malformations observed were disruptions of vertebral bodies. 5 fetuses showed cleft palates, 3 fetuses showed hepatomegaly and 1 fetus buckled ribs. The incidence for retardations and variations was increased.

In the corresponding control group 4 fetuses showed malformations. Most of the malformations observed were disruptions of vertebral bodies. 1 fetus showed buckled ribs.

After application of 1.24 µL/kg bw of the test substance 3 fetuses showed malformations (disruptions of vertebral bodies). The percentage of malformations and the incidence for retardations and variations were not increased.

In the corresponding control 2 fetuses showed malformations (disruptions of vertebral bodies).

 

In conclusion, a dose of 3.1 µL/kg bw had a toxic effect on the rats and consequently an embryolethal and fetotoxic effect. The developmental toxic effects were also due to the toxic effect on the pregnant rats. A dose of 1.24 µL/kg bw of the test substance did not cause any clinical symptoms. No embryolethal, fetotoxic or teratogenic effects were observed at this dose level.

Parameter	2.57 mg/kg bw	Untreated control 1	1.03 mg/kg bw	Untreated control 2
Pregnant dams/total dams	34/34	27/28	23/23	17/23
Implantations/dam	12.35	10.93	10.96	10.76
Living fetuses/dam	4.97	10.56	9.65	10.06
Dead fetuses	0	1	3	0
Early resorptions	60	8	16	9
Medium late resorptions	142	0	9	0
Late resorptions	33	1	2	3
Dead implantations	235**	10	30	12
% dead implantations	55.95	3.39	11.9	6.56
Abortions	16	0	-	-
Mean fetal body weight	2.39^++	3.67	3.52	3.59
Mean fetal body length	3.10^++	3.65	3.58^++	3.65
Placenta weight	0.41^++	0.56	0.48^++	0.56
Runts	161	5	4	1
Fetuses with malformations	18**	4	3	2
Skeletal malformations	12	4	2	2
Soft tissue malformations	8	0	1	0

* significance (chi-square-test) 95 %

** significance (chi-square-test) 99 %

⁺significance (t-test) 95 %

⁺⁺significance (t-test) 99 %