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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:
other: GLP Guideline

Data source

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

Materials and methods

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

Test material

Constituent 1
Chemical structure
Reference substance name:
Ammonium mercaptoacetate
EC Number:
226-540-9
EC Name:
Ammonium mercaptoacetate
Cas Number:
5421-46-5
Molecular formula:
C2H4O2S.H3N
IUPAC Name:
ammonium sulfanylacetate
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 or test system 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:
other: demineralized 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 (actual dose received)
Remarks:
2.5 mg/kg bw/day as mercaptoacetic acid
Dose / conc.:
15 mg/kg bw/day (actual dose received)
Remarks:
12.6 mg/kg bw/day as mercaptoacetic acid
Dose / conc.:
75 mg/kg bw/day (actual dose received)
Remarks:
63.3 mg/kg bw/day as mercaptoacetic acid
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 / No / No data
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 submitted to 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):
As a reaction to treatment, all rats of the high dose group showed rooting in the bedding material for about 15 minutes after dosing on different days between GD 8 and 19.
Furthermore, Hair loss was observed in 1/25 rat of the low, 6//25rats of the mid and 2/25 rats of the high dose groups. In the mid and high dose groups one rat each had a scabby skin wound. These findings are regarded as being spontaneous and not as treatment related.
Mortality:
mortality observed, treatment-related
Description (incidence):
Two animals in the high dose group died¿Atheywere found dead on GD 20
Body weight and weight changes:
no effects observed
Description (incidence and severity):
The body weight development in the low, mid and high dose groups corresponded to that in the control
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
The food consumption in the low, mid and high dose groups did not differ significantlyfrom the control
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
no effects observed
Description (incidence and severity):
The water consumption in the low and mid dose groups did not differ significantly from the control. In the high dose group the water consumption dropped significantly when the females became pregnant. This lasted until GD 9.Since the animals were treated from GD 6 to 19, thisdrop in water consumption is assumed to be coincidental and not treatment related.
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:
no effects observed
Description (incidence and severity):
The uterus weights in the low and mid dose groups were similar to the control, but were slightly and not significantly lower in the high dose group. This finding is assumed to be accicental
Gross pathological findings:
not examined
Description (incidence and severity):
Dams 88 and 89 were found dead on GD 20. The dead bodies were pale and the livers showed lobulation. All other organs were without any pathological findings. There was no indication of maltreatment. Both animals were pregnant. The fetuses weighed 2. 0 to 2.8 gram. One litter was stained and the other cut into transversal sections. The fetuses proved to be normally developed and ossified in accordance with their age and weight. A cause of death could not be established. It must be assumed that the two deaths were treatment related.
There were no abnormal findings in the other dams
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
not specified

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:
not examined
Description (incidence and severity):
Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): not examined
Changes in number of pregnant:
no effects observed
Other effects:
not specified
Details on maternal toxic effects:
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.

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
15 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
mortality
Remarks on result:
other: 12.6 mg/kg bw/day as mercaptoacetic acid

Maternal abnormalities

Abnormalities:
no effects observed

Results (fetuses)

Fetal body weight changes:
no effects observed
Description (incidence and severity):
Migrated Data from removed field(s)
Field "Fetal/pup body weight changes" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.FetalPupBodyWeightChanges): 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:
Embryotoxic / teratogenic effects:no effects

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.

Type of investigation and fndings, number of fetuses affected
Group 1
Asymmetric sternebrae 2-5 in 12111 (dam number/fetus number)
Asymmetric sternebrae 2-5 in 22/13
Group 2
Aplasia of the left testis in 47/5
Ribs bent in the paravertebral line and thickened in 48/8
Group 3
Aplasia of the righ testis in 51/12
Split sternebrae 2-4 in 62/8
Asymmetric sternebrae 2-5 in 66/3
Ribs bent in the paravertebral line and thickened in 68/8
Fetus 73/2 with an additional pair of hind extremities, grown together, originating from the abdominal wall, about 1 mm to the left of the navel. Apart from this, the appearance of the fetus is normal. Evaluation of the additional pair of hind extremities after skeletal staining: 2 rudimentary pelvic bones, growntogether, 2 femurs, tibia and fibula twice, 3 metatarsalia twice.
Group 4
Fetus 97/5 with decreased size of caudal pole of left kidney.
The type and frequency of the malformations listed above were in a normal range and not dose dependently increased.

Skeletal variations
The ossification status of the fetuses in the low, mid, and high dose groups was comparable. There was no indication of treatment related effects.

Effect levels (fetuses)

Dose descriptor:
NOAEL
Effect level:
>= 75 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Remarks on result:
other: 63.3 mg/kg bw/day as mercaptoacetic acid

Fetal abnormalities

Abnormalities:
no effects observed

Overall developmental toxicity

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 bw/d ( 2.5, 12.6 and 63.3 mg/kg bw/day as mercaptoacetic acid).

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 (12.6 mg/kg bw/day as mercaptoacetic acid) for maternal toxicity. A NOAEL has been determined at 75 mg/kg/d (63.3 mg/kg bw/day as mercaptoacetic acid) for embryo-foetal toxicity.

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