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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: Comparable to guideline study.

Data source

Reference
Reference Type:
publication
Title:
Effects of dibenzyltoluene on fetal developments of rats.
Author:
Kurosaki T, Kawashima K, Nakaura S, Tanaka S, Djajalaksana S and Takanaka A
Year:
1988
Bibliographic source:
Eisei Shikensho Hokoku 1988 ; 106 : 61-68.

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Deviations:
yes
Remarks:
some information such as the purity or batch number of the test substance or concerning the exposure conditions are lacking.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid
Details on test material:
Source: Hüls (Germany)
Batch number: no data
Purity: no data

Test animals

Species:
rat
Strain:
Wistar
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: no data
- Age at study initiation: 14 weeks for males and 12-13 weeks for females
- Weight at study initiation: no data
- Fasting period before study: no data
- Housing: individual aluminium cages for the gravid females
- Diet (e.g. ad libitum): solid diet (aliment MF, oriental yeast Co., Ltd.)
- Water (e.g. ad libitum): tap water ad libitum
- Acclimation period:


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 25 +/- 1
- Humidity (%): 55 +/- 5
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12 (6:00 to 18:00)

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
other: Sesame oil (japanese pharmacopea)
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: no data

VEHICLE
- Justification for use and choice of vehicle (if other than water): dibenzyltoluene is not soluble in water
- Concentration in vehicle: 50%
- Amount of vehicle (if gavage): 2, 06 and 0.2 ml/kg, respectively for the dose-levels of 1000, 300 and 100 mg/kg/d
- Lot/batch no. (if required): no data
- Purity: no data
Details on analytical verification of doses or concentrations:
No data
Details on mating procedure:
- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: no data
- Length of cohabitation: one night
- Proof of pregnancy: vaginal plug or sperm in vaginal smear referred to as day 0 of pregnancy
Duration of treatment / exposure:
from day 7 to day 17 of gestation
Frequency of treatment:
once a day
No. of animals per sex per dose:
20 dams
Control animals:
other: sesame oil
Details on study design:
- Dose selection rationale: The high-dose level was fixed according to preliminary assays showing a decrease in the body weight gain of gravid females given 1000 mg/kg/d of dibenzyltoluene.

Examinations

Maternal examinations:
CLINICAL OBSERVATION: daily

BODY WEIGHT: Yes
- Time schedule for examinations: daily

FOOD CONSUMPTION : Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/rat/day

WATER CONSUMPTION: No data

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on 21 day of gestation
- Organs examined: 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: Yes
- Number of implantations: Yes
- Number of : Yes
- Number of dead and liv conceptuses : Yes
Fetal examinations:
- External examinations: Yes (third per litter )
- Soft tissue examinations: Yes (third per litter ) after fixation for 2 weeks in Bouin's mixture according to the wilson's method
- Skeletal examinations: Yes (third per litter )
- Head examinations: Yes (third per litter )
- fetal weight: Yes
Statistics:
- Implantation rate: Chi-square
- Weight of dams, food consumption, number of corpora lutea, number of implants, number of fetuses, fetal body weight: Student's t test (if homogeneous variance), Aspin-Welch t test (in other cases)
- Fetal mortality, sex ratio, abnormalities frequency: Wilcoxon test.
Indices:
No data
Historical control data:
No data

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
CLINICAL FINDINGS:
Piloerection was observed in the highest dose group (1000 mg/kg/day).

MORTALITY:
Maternal mortality was not reported.

BODY WEIGHT:
A slight decrease in body weight gain was noted in dams exposed to 1000 mg/kg/day when compared to that of control.

FOOD CONSUMPTION:
A visible decrease in food intake was observed at 1000 mg/kg/day but no dose-related effect was found.

NECROPSY:
- Fertility parameters:
. All dams had live fetuses.
. A slight but statistically significant decrease in the number of corpora lutea was observed at 1000 mg/kg/day (274 corpora lutea in 20 pregnant females) when compared to control (299 corpora lutea) however since dibenzyltoluene was administered after the implantation should be performed (day 6), this effect was not considered to be treatment-related .
. Number of implants were unaffected by treatment and implant ratio was similar in all groups.

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
300 mg/kg bw/day (nominal)
Based on:
test mat.
Basis for effect level:
clinical signs
body weight and weight gain
food consumption and compound intake

Maternal abnormalities

Abnormalities:
no effects observed

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
No teratogenic effects were found.
- Mortality:
. Fetal mortality was similar in treated and control groups.
- Litters examination:
. Litter sizes in all groups were similar.
. No significant difference in sex ratio was found.
. Pups body weight was nonetheless statistically reduced in the highest dose group when compared to control (3.8 vs 4.1 g in male, 3.6 vs 3.9 g in females).
. No toxicologically significant malformations were observed.

Effect levels (fetuses)

Dose descriptor:
NOAEL
Effect level:
300 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
fetal/pup body weight changes

Fetal abnormalities

Abnormalities:
no effects observed

Overall developmental toxicity

Developmental effects observed:
yes
Lowest effective dose / conc.:
1 000 mg/kg bw/day (actual dose received)
Treatment related:
yes
Relation to maternal toxicity:
developmental effects as a secondary non-specific consequence of maternal toxicity effects
Dose response relationship:
yes
Relevant for humans:
not specified

Applicant's summary and conclusion

Conclusions:
Under these experimental conditions, the No-Observed-Adverse-Effect-Level (NOAEL) was 300 mg/kg/d for maternal and foetal toxicity.
Executive summary:

The potential of dibenzyltoulene to induce developmental toxicity after maternal exposure during the critical period of organogenesis was evaluated in rat according to a study design comparable to OECD Guideline N° 414.

Dibenzyltoluene was administered orally by gavage to three groups of 20 bred female Sprague-Dawley rats once daily from gestation days 7 through 17. Dosage levels were 0, 100, 300 and 1000 mg/kg/d.

Animals were observed daily for mortality and morbidity. Clinical observations, body weights and food consumption were recorded at appropriate intervals.

On gestation day 20, a hysterectomy was performed on each female. The uteri, placenta and ovaries were examined, and the number of foetuses, resorptions, total implantations, and corpora lutea were recorded. Gravid uterine weights were recorded. The foetuses were weighted, sexed and examined for external, visceral and skeletal malformations and developmental variations.

All animals survived to the scheduled necropsy. Piloerection was observed in females given 1000 mg/kg/d as well as a slight decrease in body weight gain and food consumption.

The slight increase in the resorption of corpora lutea noted in the highest dose group was not considered as relevant since the administration of dibenzyltoluene occurred after the implantation. The survival of the pups was unaffected by dibenzyltoluene administration at all dose levels. However, pups body weight was reduced in the highest dose group when compared to controls but this effect was related to the maternal toxicity observed. Foetal external, soft tissue and skeletal malformations observed in control and treated pups were considered to be spontaneous in origin. 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.

Under these experimental conditions, the No-Observed-Adverse-Effect-Level (NOAEL) was 300 mg/kg/d for maternal and fetal toxicity.