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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:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1998
Report Date:
1998

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Test substance: Ammonium thioglycolate (71%)
Source: Merck KGaA
Batch: U1499277
Content of active ingredient: 71.5%

Test animals

Species:
rat
Strain:
Wistar
Details on test animals and environmental conditions:
Strain of rats: Hsd/Cpb: WU
Source: Fa. Harlan Winkelmann GmbH, 33178 Borchert
Age: 9-10 weeks old
Acclimatization period: 6 days
Weight range at study initiation: 177-213 g Diet: Altromin Standard Diet TPF N 1234, ad libitum
Water: Tap water, ad libitum

Husbandry:
Housing: Makrolon type III cages
Illumination: artificial lighting from 6.00 a.m. - 6.00 p.m.
Temperature: 21-23.5°C
Relative humidity: 51-66%Vehicle: demineralized water

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
water
Details on exposure:
- Rate of solution preparation: daily
- Amount of vehicle: 10 ml/kg (base on weight on GD6)
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The concentration and homogeneity of ammonium thioglycolate in preparations administred were determined once during the study, on the second day of treatment. The results showed values ranging from 96.5 % to 100 % of the nominal concentrations
Details on mating procedure:
- Groups of four sexually matures, virgin females were left over night with one stock stud.
- Proof of pregnancy: sperm in vaginal smear (GD 0)
Duration of treatment / exposure:
gestation days 6 - 19
Frequency of treatment:
daily
Duration of test:
Duration of test: 15 days - dosing GD 6 -19, animals were killed on day 20
Doses / concentrationsopen allclose all
Dose / conc.:
3 mg/kg bw/day
Dose / conc.:
15 mg/kg bw/day
Dose / conc.:
75 mg/kg bw/day
No. of animals per sex per dose:
25
Control animals:
yes, concurrent vehicle

Examinations

Maternal examinations:
Clinical signs including mortality and evidence of abortion were checked daily.
Body weight was determined on GD0, 6 and daily until GD20.
Food and water consumption were recorded at designated intervals during pregnancy.
On day 20 of pregnancy, females were killed. The terminal body weights of the dams were recorded. Females were examined macroscopically.

Litter parameters were recorded: number of corpora lutea, implantation sites, early and late resorptions, and dead and live foetuses.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes:
Fetal examinations:
Foetuses were weighed, sexed, and submittedto external examination. About 1/2 of them were examined for skeletal malformations and 1/2 for organ malformations.The foetus sex was determined on the base of measurment of anogenital indice and by inspection of gonads.
Statistics:
yes: Dunnett test or Fischer-Pitman permutation test

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
see below
Mortality:
mortality observed, treatment-related
Description (incidence):
see below
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
no effects observed
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:
no effects observed
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
not specified
Details on results:
Rooting in the bedding material was seen in all rats in the high dose group. Two animals in the high dose group died on GD 20, one day after the last administration of the test material. These deaths are regarded to be treatment related.
18 to 24 rats out of 25 per group proved to be pregnant.
The body weight development, food and water consumption were not affected by treatment. The terminal body weights were similar in all groups.
The uterus weights in the high dose group were slightly, but not significantly lower than in the control or the other groups. This finding is regarded to be accidental. The numbers of corpora lutea, implantations and live foetuses were not affected.
The numbers of dead foetuses, complete, early and late resorptions were not increased. The sex distribution was not affected in any of the groups.

Maternal developmental toxicity

Number of abortions:
no effects observed
Pre- and post-implantation loss:
no effects observed
Total litter losses by resorption:
no effects observed
Early or late resorptions:
no effects observed
Dead fetuses:
no effects observed
Changes in pregnancy duration:
no effects observed
Changes in number of pregnant:
no effects observed
Other effects:
no effects observed

Effect levels (maternal animals)

open allclose all
Key result
Dose descriptor:
NOAEL
Effect level:
15 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
clinical signs
mortality
Key result
Dose descriptor:
LOAEL
Effect level:
75 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
clinical signs
mortality

Maternal abnormalities

Key result
Abnormalities:
no effects observed

Results (fetuses)

Fetal body weight changes:
no effects observed
Reduction in number of live offspring:
no effects observed
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
not examined
External malformations:
no effects observed
Skeletal malformations:
no effects observed
Visceral malformations:
no effects observed
Other effects:
not specified
Details on embryotoxic / teratogenic effects:
The weights of the foetuses in the low, mid, and high dose groups were similar to the control and not affected by treatment. The frequency of all malformations was in a normal range and not increased.

Effect levels (fetuses)

open allclose all
Key result
Dose descriptor:
NOAEL
Effect level:
>= 75 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Remarks on result:
not determinable due to absence of adverse toxic effects
Key result
Dose descriptor:
LOAEL
Effect level:
> 75 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Remarks on result:
not determinable due to absence of adverse toxic effects

Fetal abnormalities

Key result
Abnormalities:
no effects observed

Overall developmental toxicity

Key result
Developmental effects observed:
no

Applicant's summary and conclusion

Conclusions:
The doses of 3 and 15 mg ammonium thioglycolate/kg were systemically tolerated by the rats.
At dose level of 75 mg/kg, two dams died on GD 20. Rooting in the bedding material had been seen, but no maternotoxic effects.
The no observed effect level (NOEL) for embryo-fetal toxicity was 75 mg/kg.
No teratogenic effects were observed.
Executive summary:

The potential of ammonium mercaptoacetate to induce developmental toxicity after maternal exposure during the critical period of organogenesis was evaluated in rat according to OECD Guideline N° 414 (22nd January 2001) and in compliance with Good Laboratory Practices.

Ammonium mercaptoacetate was administered orally by gavage to four groups of 25 bred female Sprague-Dawley rats once daily from gestation days 6 through 19. Dosage levels were 0, 3, 15, and 75 mg/kg/d.

The fetuses were delivered by caesarean section on GD 20 and examined for macroscopic malformations. About 1/2 of them were examined for skeletal malformations and 1/2 for organ malformations. Clinical signs including mortality and evidence of abortion were checked daily. Body weight was determined on GD0, 6 and the daily until GD20. Food and water consumption was recorded at designated intervals during pregnancy. On day 20 of pregnancy, females were killed. The terminal body weights of the dams were recorded. The gravid uterus was weighed and foetuses removed by hysterectormy. Females were examined macroscopically.

The doses of 3 and 15 mg ammonium thioglycolate/kg were systemically tolerated by the rats. All animals in the low and medium level dose group survived to the scheduled necropsy. At the dose level of 75 mg/kg, two dams died on GD20, one day after the last administration of test material. These death were considered treatment related. At this dose level, rooting in the bedding material had been seen in all rats, but no maternotoxic effects. No treatment related internal findings were observed at any dose level. No clinical signs that could be attributed to ammonium mercaptoacetate were observed in the treated groups. Body weight and food consumption were not affected by treatment. Intrauterine growth and survival were unaffected by ammonium mercaptoacetate administration at all dose levels. Any significant or relevant foetal external, soft tissue and skeletal malformations were observed at any dose level. The developmental variations expressed in the treated groups were generally similar to those present in the control group or occurred in a manner that was not dose related. No teratogenic effects were observed

Under these experimental conditions, the No-Observed-Adverse-Effect-Level (NOAEL) was 15 mg/kg/d for maternal toxicity. A NOAEL has been determined at 75 mg/kg/d for embryo-foetal toxicity.