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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

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
1981
Report Date:
1981
Reference Type:
publication
Title:
Teratology studies on benzothiazolesulfenamides
Author:
Levinskas, G.J.
Year:
1982
Bibliographic source:
The Toxicologist 2, 73

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:
Groups of 25 pregnant females were treated by gavage with CBS at dose levels of 100, 300, 500, and 900 mg/kg bw and day during gestation day 6 to 15. Cesarean sections were performed on all surviving dams on gestation day 20.
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Test substance: Santocure CBS

Test animals

Species:
rat
Strain:
other: Charles River COBS CD

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on mating procedure:
M/F ratio per cage: 1:1
Duration of treatment / exposure:
6th to 15th day of pregnancy
Frequency of treatment:
Daily
Duration of test:
GD 20 (scheduled sacrifice)
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day
Remarks:
Control
Dose / conc.:
100 mg/kg bw/day
Dose / conc.:
300 mg/kg bw/day
Dose / conc.:
500 mg/kg bw/day
Dose / conc.:
900 mg/kg bw/day
No. of animals per sex per dose:
25 females per dose
Control animals:
yes
Details on study design:
Sex: female

Examinations

Maternal examinations:
appearance and behaviour, body weights, Cesarean section observations, fetal morphology observations.
Ovaries and uterine content:
Immediately following sacrifice, the uterus was excised and weighed prior removal of the fetuses. The umber and location of viable and nonviable fetuses, early and late resorptions and number of total inplantations and corpora lutea were recorded.
Fetal examinations:
All fetuses were individually weighed and examined for external malformations and variations, including palate and eyes. Approximaetly one half of the fetuses were used for visceral examinations and the other for skeletal examinations.
Statistics:
Male and female sex distribution and the number of litters with malformations were compared using the Chi-square test criterion, Fisher's exact probability test; number of early and late resorptions and postimplantation loss were compared by the Mann-Whitney U-test; the mean number of viable fetuses, total implantations, corpora lutea and mean fetal body weights were compared by anaylsis of variance (one-way classification).
Historical control data:
Yes.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Due to the early deaths of 5 rats and due to signs of excessive maternal toxicity and weight loss in the remaining animals, the rats in the 900 mg/kg7day dosage group were sacrificed and discarded.
Mortality:
mortality observed, treatment-related
Description (incidence):
Due to the early deaths of 5 rats and due to signs of excessive maternal toxicity and weight loss in the remaining animals, the rats in the 900 mg/kg7day dosage group were sacrificed and discarded.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Due to the early deaths of 5 rats and due to signs of excessive maternal toxicity and weight loss in the remaining animals, the rats in the 900 mg/kg7day dosage group were sacrificed and discarded. A severe decrease in in mean maternal body weight occurred in the 500 mg/kg/day group and a slight to moderate decrease in mean maternal body weight was noted in the 300 mg/kg/day dosage group during the treatment period.
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
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 specified
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
There were no remarkable necropsy findings in those females surviving to the scheduled sacrifice with the exception of one non-gravid rat with hdyrometra. in the 300 mg/kg/day dosage group.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
no effects observed

Maternal developmental toxicity

Number of abortions:
no effects observed
Description (incidence and severity):
There were no meaningful differences in the mean numbers of corpora lutea, total implantations, postimplantation loss, vialble fetuses or the fetal sex distribution in rats in any of the treated groups when compared to the control group.
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
There were no meaningful differences in the mean numbers of corpora lutea, total implantations, postimplantation loss, vialble fetuses or the fetal sex distribution in rats in any of the treated groups when compared to the control group.
Total litter losses by resorption:
no effects observed
Description (incidence and severity):
There were no meaningful differences in the mean numbers of corpora lutea, total implantations, postimplantation loss, vialble fetuses or the fetal sex distribution in rats in any of the treated groups when compared to the control group.
Early or late resorptions:
no effects observed
Description (incidence and severity):
There were no meaningful differences in the mean numbers of corpora lutea, total implantations, postimplantation loss, vialble fetuses or the fetal sex distribution in rats in any of the treated groups when compared to the control group.
Dead fetuses:
no effects observed
Description (incidence and severity):
There were no meaningful differences in the mean numbers of corpora lutea, total implantations, postimplantation loss, vialble fetuses or the fetal sex distribution in rats in any of the treated groups when compared to the control group.
Changes in pregnancy duration:
no effects observed
Description (incidence and severity):
There were no meaningful differences in the mean numbers of corpora lutea, total implantations, postimplantation loss, vialble fetuses or the fetal sex distribution in rats in any of the treated groups when compared to the control group.
Changes in number of pregnant:
no effects observed
Description (incidence and severity):
There were no meaningful differences in the mean numbers of corpora lutea, total implantations, postimplantation loss, vialble fetuses or the fetal sex distribution in rats in any of the treated groups when compared to the control group.
Other effects:
no effects observed

Effect levels (maternal animals)

open allclose all
Dose descriptor:
NOAEL
Effect level:
100 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
other: maternal toxicity
Dose descriptor:
LOAEL
Effect level:
300 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
other: maternal toxicity

Results (fetuses)

Fetal body weight changes:
effects observed, treatment-related
Description (incidence and severity):
a slight decrese in mean fetal body weight was observed in the 100 and 300 mg/kg/day dosage groups when compared to the control group, with a statistical significant decrease in the 500 mg/kg/day dosage group.
Reduction in number of live offspring:
no effects observed
Description (incidence and severity):
There were no meaningful differences in the mean numbers of corpora lutea, total implantations, postimplantation loss, vialble fetuses or the fetal sex distribution in rats in any of the treated groups when compared to the control group.
Changes in sex ratio:
no effects observed
Description (incidence and severity):
There were no meaningful differences in the mean numbers of corpora lutea, total implantations, postimplantation loss, vialble fetuses or the fetal sex distribution in rats in any of the treated groups when compared to the control group.
Changes in litter size and weights:
no effects observed
Description (incidence and severity):
There were no meaningful differences in the mean numbers of corpora lutea, total implantations, postimplantation loss, vialble fetuses or the fetal sex distribution in rats in any of the treated groups when compared to the control group.
Changes in postnatal survival:
no effects observed
Description (incidence and severity):
There were no meaningful differences in the mean numbers of corpora lutea, total implantations, postimplantation loss, vialble fetuses or the fetal sex distribution in rats in any of the treated groups when compared to the control group.
External malformations:
no effects observed
Description (incidence and severity):
There were no statistically significant differences in the number of litters with malformations in any of the treated groups when compared to the control group.
Skeletal malformations:
no effects observed
Description (incidence and severity):
There were no statistically significant differences in the number of litters with malformations in any of the treated groups when compared to the control group.
Visceral malformations:
no effects observed
Description (incidence and severity):
There were no statistically significant differences in the number of litters with malformations in any of the treated groups when compared to the control group.
Description (incidence and severity):
a very slight increase in the number of fetuses and litters with malformations was noted in the 500 mg/kg/day dosage group when compared to the control group. This increase was due primarily to 3 fetuses, each from a different litter, with a thread-like tail and a smal anus. The only malformed fetus in the 100 mg/kg/day dosage group also had a thread-like tail and a small anus.
there were no biologically meaningful differences or dose-related trends in the number of fetuses or litters with genetic and developmental variations in any treated group when compared to the control group.
Details on embryotoxic / teratogenic effects:
treatment with Santocure did not produce a teratogenic response when administered to pregant Charles River COBS CD rats at a dosage level of 500 mg/kg/day or less.

Effect levels (fetuses)

open allclose all
Key result
Dose descriptor:
NOAEL
Effect level:
300 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: fetotoxicity
Key result
Dose descriptor:
LOEL
Effect level:
500 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: fetotoxicity

Fetal abnormalities

Key result
Abnormalities:
no effects observed

Overall developmental toxicity

Key result
Developmental effects observed:
yes
Lowest effective dose / conc.:
500 mg/kg bw/day
Treatment related:
yes
Relation to maternal toxicity:
developmental effects as a secondary non-specific consequence of maternal toxicity effects
Dose response relationship:
yes

Any other information on results incl. tables

Maternal toxicity

900 mg/kg bw/day:

Appearance and behavior: Matting and yellow or red staining of the anogenital region were observed in 23 of 25 rats in the 900 mg/kg bw/day group. Red and chalky urine, a severe red nasal discharge, mucoid ocular discharge, soft stool or hair loss were noted on many rats.

Mortality: 5/25 rats died between gestation days 10 and 12, three of these showing signs of convulsions prior to death. Observations at necropsy on these five rats included: two rats with mucoid ocular discharge and hyperemic bladder mucosa or cecum mucosa; one with slightly congested brain vessels; two with congested lungs; one with mucoid contents in the small intestine and two with a severe, red nasal discharge. Pneumonia was considered a cause of death for 1 dam. A cause of death could not be determined for the remaining animals that died. The remaining 20 rats in the 900 mg/kg bw dosage group were sacrificied between gestation days 11 and 14 due to excessive maternal toxicity.

Body weight gain: serve decreased prior to sacrifice

500 mg/kg bw/day:

mortality: 1/25 (one animal died on gestation day 9. Observations at necropsy revealed a congested thymus and black, fluid contents in the stomach. (No cause of death could be determined for this female).

Matting and/or staining of the vantral surface or anogenital region (noted also in the control (2/25) but with the greatest incidence occuring in the 300 and 500 mg/kg bw/day groups (17/25 rats), hair loss occured in all treatment groups but most frequently at 500 mg/kg bw/day

Body weight gain: serve decrease during the treatment period, slightly reduced body weight gain folowing the treatment period and severely reduced adjusted body weights on gestation day 20

Cesaren section observations: no biologically relevant differences in postimplantation loss or the fetal sex distribution compared to control; however statistically significant decrease in the mean number of corpora lutea, mean number of total implantations and viable fetuses. These findings were considered as not biologically relevant since implantation occurred before test article administration began and the values were within the range established in the historical control data.

300 mg/kg bw/day:

survival: 100 %

Matting and/or staining of the vantral surface or anogenital region (noted also in the control (2/25) but with the greatest incidence occuring in the 300 and 500 mg/kg bw/day groups (12/25 rats)

Necropsy: there were no remarkable necropsy findings in those females surviving to the scheduled sacrifice, with one exception (1/25 non- gravid rats with hydrometra)

Body weight gain: a slight to moderate decrease during the treatment period; adjusted body weights on gestation day 20 were comparable to control

Cesaren section observations: no biologically relevant differences in the mean number of corpora lutea, total implantations, postimplantation loss or viable fetuses or compared to control; however statistically significant differences in the fetal sex distribution; however was attributed to random occurence and was not considered compound relevant.

100 mg/kg bw/day:

Survival: 100 %

No meaningful difference in the appearance or behavior of rats of the 100 mg/kg bw/day group compared to control

Matting and/or staining of the vantral surface or anogenital region (2/25; control 2/25)

Necropsy: there were no remarkable necropsy findings

Body weight gain: no effects

Cesaren section observations: no biologically relevant differences in the mean number of corpora lutea, total implantations, postimplantation loss, viable fetuses or the fetal sex distribution compared to control

Fetal toxicity:

500 mg/kg bw/day:

Statistically significant decrease in mean fetal body weight; these findings were considered as biologically relevant (values were less than of both control groups and historical control data)

Fetal morphological observations:

There were no statistically significant differences in the number of litters with malformation, however a very slight increase in the number of fetuses and litters with malformation was noted; due primarly to 3 fetuses, each from a different litter, with a thread-like tail and a small anus.

300 mg/kg bw/day:

Slight decrease in mean fetal body weight

Fetal morphological observations:

There were no statistically significant differences in the number of litters with malformation

100 mg/kg bw/day:

Slight decrease in mean fetal body weight

Fetal morphological observations:

There were no statistically significant differences in the number of litters with malformation, however 1 fetus had a thread-like tail and a small anus

Remarks:

There were no biologically relevant differences or dose-related trends in the number of fetuses or litters with genetic and developmental variations in any treated group when compared to control group. The occurence of fetuses with a thred-like tail and small anus has previously been observed in litters of control animals in this laboratory. The author concluded that the increase in frequency of fetuses with a thred-like tail and small anus reported in the study may be due to an increase incidence of genetic expression of this condition among female rats used in this study and occurred at a level which exhibited frank materal toxicity.

Applicant's summary and conclusion

Conclusions:
The NOAEL derived from this study for maternal toxicity is 100 mg/kg bw and day and is based on a decrease in mean body weight gain. The NOAEL for the offspring is 300 mg/kg bw and day and is based on a decrease mean foetal body weight.
Executive summary:

In a guideline-consistent developmental toxicity study (Monsanto 1981) which was performed with Charles River COBS CD rats, groups of 25 pregnant females were treated by gavage with CBS at dose levels of 100, 300, 500, and 900 mg/kg bw and day during gestation day 6 to 15. The control group received corn oil. Due to excessive toxicity and death the 900 mg/kg bw and day dose group had to be ceased before end of the study. One maternal death and severe decrease in mean maternal body weight gain and adjusted body weight on gestation day 29 were observed at the 500 mg/kg dose level. A slight to moderate decrease in mean maternal body weight gain was noted in the 300 mg/kg dose group. Hair-loss was noted in all groups, most frequently in the 500 mg/kg dose group. There were no dose-dependent and biologically meaningful effects on mean numbers of corpora lutea, total implantations, post-implantation loss, viable foetuses, or foetal sex distribution in any of the treated groups when compared to controls. There were a very slight increase in the number of foetuses and litters with malformations in the 500 mg/kg dose group due to primarily to three foetuses, each from a different litter, with a thread-like tail and small anus. However, overall, there were no statistically significant differences in the number of litters with malformations in any of the treated groups when compared to the control groups. Further effects observed in the offspring were related to foetal body weight. A slight decrease in mean foetal body weight was observed in the 100 and 300 mg/kg dose group which was statistically significant different from controls for the 500 mg/kg bw and day dose group. The NOAEL derived from this study for maternal toxicity is 100 mg/kg bw and day and is based on a decrease in mean body weight gain. The NOAEL for the offspring is 300 mg/kg bw and day and is based on a decrease mean foetal body weight.