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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1989
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: A well reported which shows clear evidence of developmental toxicity. No data on the purity of the test substance provided. Some of testing may have been sequential rather than concurrent.

Data source

Reference
Reference Type:
publication
Title:
Effects of 2-methoxyethanol on fetal development, postnatal behaviour and embryonic intracellular pH of rats,
Author:
Nelson BK, Vorhees CV, Scott WJ et al
Year:
1989
Bibliographic source:
Neurotoxicol Teratol, 11, 273-84

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Principles of method if other than guideline:
Dams exposed to substance in liquid diet during key part of gestation period, terminated on day 20 then fetuses removed and examined for teratogenic and other developmental effects. Core requirements of above guideline followed (apart from treatment period and some parameters not reported in publication) with additional examinations added.
GLP compliance:
not specified
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
No data.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories (Portage, MI)
- Weight at study initiation: 200-300g
- Housing: individual, except during mating in hanging metal cages.
- Diet: Purina lab chow, except during gestation days 7-18 was a administered liquid Sustacal and sucrose based liquid diet (formulation provided) dosed with test compound. Diet administered from bottles designed to minimise evaporation. Diet refreshed daily with new material.
- Water: available ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature: 22+/-2C
- Humidity: 40-60%
- Photoperiod: 12hrs dark/12hrs light

Administration / exposure

Route of administration:
other: liquid diet
Vehicle:
other: Not Applicable
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Rate of preparation of diet (frequency): mixed every 2-3 days.
Solutions prepared by replacing water used in the diet make up with the test substance.
Storage temperature of food: refrigerated.
Analytical verification of doses or concentrations:
no
Details on mating procedure:
Verification of same strain and source: Males obtained from same supplier as females.
Proof of pregnancy: sperm plug, presence of which defined day 0.
Duration of treatment / exposure:
GD 7-18
Frequency of treatment:
ad libitum. Consumption of diet recorded daily during treatment.
Duration of test:
To GD20 when dams terminated (CO2 asphyxiation) and fetuses removed.
No. of animals per sex per dose:
10
Control animals:
yes
Details on study design:
- Dose selection rationale: Previous research. Doses were progressively decreased until a no effect level was observed.

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes, no further data

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: days 0, 7, 14, 20

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
- Food consumption reported as average per dose level
- Compound intake calculated as time weighted average from consumption and body weight data: Yes, resulting in estimated dose of 16, 31, 73, 140, 198, 290, 620 mg/kg/day.

POST-MORTEM EXAMINATIONS: No data
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: No data
- Number of implantations: Yes
- Number of resorptions: Yes
Fetal examinations:
- External examinations: Yes: all per litter, including sexing
- Soft tissue examinations: Yes: 67% of litter after fixing in Bouin’s solution and using Wilson technique.
- Skeletal examinations: Yes: 33% of litter, using a modified doubles staining technique.
- Head examinations: No data
Statistics:
Parametric method with litter as N and p<0.5 for significance. Post hoc comparison using Duncan’s multiple range test. When repeated measures analysis of variance was used and significant interaction terms were present, the Geisser-Greenhouse F-ratio was used as a correction.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
Animals receiving doses of 0.05% and above produced significantly lower body weight gain and dietary consumption was significantly lower at doses of 0.1% and above.
Clinical observations:
At 0.5% dams showed diarrhea, respiratory difficulties, eye and nose exudate, allopecia, lack of grooming and general malaise. Effects were less marked at 0.25% with only malaise and ungroomed appearance being noted. There were no adverse observations with the 0.1% group.

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
0.025 other: % (73mg/kgbw)
Basis for effect level:
other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
All litters were resorbed from the 0.05% group and above. From the 0.025% dose group, 4/9 litters were totally resorbed and only 10 live fetuses survived from the remaining 5 litters. No external malformations were observed in the 3 fetuses examined for skeletal defects but 4/7 soft tissue malformations were observed in the other fetus. Two, from different litters, showed oesophageal and tracheal stenosis, misplaced ductus arteriosus and double and/or misplaced aortic arch. One had a ventricular septal defect. Two other fetuses (same litters as above) showed the aortic arch defect. The 0.012% dose group showed resorption levels comparable to controls. No external malformations were observed. One litter had two pups with aortic arch defects and wavy, rudimentary and fused ribs. Fetal weight remained significantly below controls. At 0.006%, the lowest dose tested, no soft tissue or skeletal defects noted and resorptions were at control levels. However, fetal weight remained slightly but significantly (12-15%) below levels for controls.

Effect levels (fetuses)

open allclose all
Dose descriptor:
NOAEL
Effect level:
< 0.006 other: % (26mg/kgbw)
Basis for effect level:
other: fetotoxicity
Dose descriptor:
NOAEL
Effect level:
0.006 other: %
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

The steepest part of the dose response curve is 30-40mg/kg/day under this exposure regime.

Applicant's summary and conclusion

Executive summary:

Methoxyethanol when administered in a liquid diet to pregnant female rats during GD7-18 produced both teratogenic and fetotoxic effects. The most sensitive effect being fetotoxicity, manifest as a slight but significant reduction in pup weight of 12-15% at the lowest dose tested of 0.006% (equivalent to 26mg/kg/day.)  The no effect level for teratogenic effects was 0.006% and for maternal toxicity 0.025% (73mg/kg/day).