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Toxicological information

Toxicity to reproduction

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Administrative data

Endpoint:
screening for reproductive / developmental toxicity
Remarks:
Study is essentially a developmental toxicity study but has a postnatal development phase.
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Circa 1988
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1988

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Essentially a developmental toxicity study but with a number females allowed to deliver their offspring and their postnatal growth and development monitored.
GLP compliance:
no
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Specific details on test material used for the study:
Dihydroacetic acid sodium salt (DHA-Na) referred to as sodium dehydroacetate in the publication.

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals and environmental conditions:
Wistar rats (Japanese Rat), 12 to 13 weeks old. Cohabitated nulliparous females and males were paired overnight to achieve conception. For females presenting with sperm on the vaginal smear on the following morning for the experiment this was designated as gestation day 0 (GD 0). The females were housed in individual aluminium pregnancy cages (manufactured by Natsume Seisakusho Co., Ltd.), and were allowed free access to solid feed (Oriental Yeast Co., Ltd., MF) and tap water. The animal rearing laboratory was kept at 25 ± 1oC, 55 ± 5% relative humidity, ventilated 15 times/hr. and under a 12 hours of light regimen (6:00 to 18:00).

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
water
Details on exposure:
Gestation days (GD) 6 to 17.
Details on mating procedure:
Cohabitated nulliparous females and males overnight to achieve conception.
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
Gestation days (GD) 6 to 17.
Frequency of treatment:
Daily Gestation days (GD) 6 to 17.
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day (nominal)
Dose / conc.:
25 mg/kg bw/day (nominal)
Dose / conc.:
50 mg/kg bw/day (nominal)
Dose / conc.:
100 mg/kg bw/day (nominal)
No. of animals per sex per dose:
22
Control animals:
yes, concurrent vehicle
Positive control:
No

Examinations

Parental animals: Observations and examinations:
Clinical observations, body weight, food consumption.
Oestrous cyclicity (parental animals):
Not examined.
Sperm parameters (parental animals):
Not examined.
Litter observations:
From day of birth to 10 weeks of age of the offspring. Clinical observations, body weight.
Postmortem examinations (parental animals):
Necropsy, macroscopic examination.
Postmortem examinations (offspring):
Necropsy, macroscopic examination, organ weights.
Statistics:
Dams were considered to be the the unit of evaluation for the experimental results; Chi square-tests, t-tests and signed rank sum tests, results compared to the control group; hazard ratios of 5% and 1% were considered significant.
Reproductive indices:
Not specified.
Offspring viability indices:
Not specified, but offspring viability findings are clearly indicated by the data.

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Piloerection at 100 mg/kg bw/day from GD 9. Not observed on GD 20.
Dermal irritation (if dermal study):
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
At 100 mg/kg bw/day: significantly reduced at GD 15, 18 and 20. See tabulated data attached. See tabulated data attached.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
At 100 mg/kg bw/day: significantly reduced at GD 12, 15 and 18. See tabulated data attached.
At 50 mg/kg bw/day: tansistory reduction at GD 12 and 18 - not reduced GD 15 or 20. See tabulated data attached.
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):
no effects observed
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
not specified
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
not specified

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:
not examined
Reproductive function: sperm measures:
not examined
Reproductive performance:
no effects observed

Effect levels (P0)

open allclose all
Dose descriptor:
LOAEL
Effect level:
ca. 100 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
female
Basis for effect level:
body weight and weight gain
food consumption and compound intake
Key result
Dose descriptor:
NOAEL
Effect level:
> 50 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
female
Basis for effect level:
other: No significant maternal or embryo-fetal toxicity at 50 mg/kg bw/day.

Target system / organ toxicity (P0)

Key result
Critical effects observed:
not specified

Results: F1 generation

General toxicity (F1)

Clinical signs:
no effects observed
Dermal irritation (if dermal study):
no effects observed
Mortality / viability:
mortality observed, non-treatment-related
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not examined
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 specified
Sexual maturation:
no effects observed
Description (incidence and severity):
The offspring were weighed weekly and examined daily for 10 weeks, no observations were made regarding abnormal sexual development.
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings:
not examined
Other effects:
not specified

Developmental neurotoxicity (F1)

Behaviour (functional findings):
no effects observed

Developmental immunotoxicity (F1)

Developmental immunotoxicity:
not examined

Effect levels (F1)

Key result
Dose descriptor:
NOAEL
Generation:
F1
Effect level:
> 100 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No significant embryo-fetal or F1 offspring toxicity at 100 mg/kg bw/day.

Target system / organ toxicity (F1)

Key result
Critical effects observed:
no

Overall reproductive toxicity

Key result
Reproductive effects observed:
no

Applicant's summary and conclusion

Conclusions:
At 100 mg/kg bw/day: Maternal toxicity was evident as reduced food intake and body weight performance (there were also some changes in food intake ay 50 mg/kg bw/day). Additionally, in the females killed at GD 20, for examination of their uterine content, early resorptions were higher and late resorptions marginally high. Fetal body weight was also low and decreased ossification was observed for some skeletal elements. There were no other treatment related effects at this dosage.
DHA-Na was not teratogenic. For the parental (P0) females, that gave birth naturally, and their progeny, no treatment related effects were seen at any treatment level. All litters developed normally as expected until 10 weeks postpartum when the study was terminated. In utero treatment with DHA-Na up to 100 mg/kg bw/day was without effect on the F1 progeny.
Executive summary:

Groups of 22-23 female rats were treated with DHA-Na at 0, 25, 50 or 100 mg/kg bw/day throughout gestation (GD 6 -17). 16-17 females were selected for uterine exanimation at GD 20 and the remaining females were allowed to give birth naturally and raise their litters. The F1 offspring remained on study for 10 weeks. At 100 mg/kg bw/day: Maternal toxicity was evident as reduced food intake and body weight performance (there were also some changes in food intake ay 50 mg/kg bw/day). Additionally, in the females killed at GD 20, for examination of their uterine content, early resorptions were higher and late resorptions marginally high. Fetal body weight was also low and decreased ossification was observed for some skeletal elements. There were no other treatment related effects at this dosage. DHA-Na was not teratogenic. For the parental (P0) females, that gave birth naturally, and their progeny, no treatment related effects were seen at any treatment level. All litters developed normally as expected until 10 weeks postpartum when the study was terminated. In utero treatment with DHA-Na up to 100 mg/kg bw/day was without effect on the F1 progeny.

The effects seen on the fetuses at 100 mg/kg bw/day (and to a lesser extent at 50 mg/kg bw/day) were most likely because of maternal toxicity. This was further illustrated by the females that were allowed to litter, where the F1 offspring survival and development were unaffected by treatment.