Phenol, 2,4-bis[(dodecylthio)methyl]-6-methyl-

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

1987 - 1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP and OECD guideline compliant study. According to ECHA guidance, a study with a read-across substance can have no better reliability score than 2. The study itself is valid without restrictions.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1988

Report date:

1988

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Details on test material:

- Physical state: liquid
- Analytical purity: 92.1%
- Purity test date: 1987-03-05
- Lot/batch No.: 31-33
- Expiration date of the lot/batch: September 1991
- Stability under test conditions: stable
- Storage condition of test material: The test article was stored at room temperature in a dark area away from heat.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Wiga GmbH, 8741 Sulzfeld, West Germany
- Age at study initiation: 8 - 12 weeks
- Weight at study initiation: 180 to 245 g
- Housing: Prior to mating and during mating, the female rats were housed in groups of twenty to twenty-five in communal cages.Mated female rats were individually housed in solid floor macrolone cages of type II with stainless steel lids (dimensions: 260 mm x 200 mm x 140 mm; E. Becker & Co GmbH, 4620 Castrop-Rauxel, West Germany).
- Diet: ad libitium
- Water: ad libitium
- Acclimation period: one week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25 °C
- Humidity (%): 40 to 70%
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 19.03.1987 To: 23.04.1987 (date of last necropsy)

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

arachis oil

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples for analysis were taken from dose formulations prepared for each dose level on 27.03.1987 (beginning of treatment), deep-frozen immediately after formulation, and sent to the study sponsor for analysis in dry ice, inadvertently not before 15.07.1987. Based on the analytical data, it was concluded that the test article was sufficiently stable during the application period.

Details on mating procedure:

The male and female animals were mated at a ratio of 1 : 4 in communal cages during the night.
The females were examined on the following morning for the presence of sperm and/or a vaginal plug.
The day on which sperm and/or a vaginal plug were observed was designated day 0 of gestation.

Duration of treatment / exposure:

Day 6 to 15 post-coitum (inclusive)

Frequency of treatment:

daily

Duration of test:

Day 6- 15 with treatment, maintained without treatment until day 20 post-coitum and were sacrificed and examined on that day.

Doses / concentrations

Remarks:

Doses / Concentrations:
50, 150 and 300 mg/kg bw
Basis:
actual ingested

No. of animals per sex per dose:

25

Control animals:

yes, concurrent vehicle

Details on study design:

Dose selection rationale: Based on the results of a screening study (Report no. 614-380/42,dated March 1986)

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily
- Cage side observations :signs of ill-health, toxicity, behavioural change, mortality

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: see above

BODY WEIGHT: Yes
- Time schedule for examinations: The body weight of each inseminated female rat was recorded on days 0, 6 to 15, and 20 post-coitum and evaluated for days 0, 6, 10, 15, and 20 postcoitum.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
The food consumption of each inseminated female rat was recorded for days 0 to 6, 6 to 10, 10 to 15, and 15 to 20 post-coitum.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: any abnormalities were recorded.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: Individual foetal weights and sex of the foetuses

Intra-uterine deaths were classified as follows:
Early resorptions showed decidual or placental tissues only.
Late resorptions showed embryonic or foetal tissue in addition to placental tissue but excluded foetuses dying in utero within approximately two days
prior to the terminal kill. Dead foetuses included only the foetuses dying in utero within approximately the last two days.

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: see below

Half of the foetuses from each litter (taking every second foetus in accordance with the position in the uterine horn, if possible) were eviscerated
and preserved in 95 per cent ethanol for determination of skeletal abnormalities (Alizarin staining technique).
The remaining half was fixed in Bouin's fixative for determination of vis ceral abnormalities (Wilson technique).
The uteri of apparently non-pregnant females were immersed in a 10 per cent solution of ammonium sulphide to reveal evidence of implantation (Salewski technique).

Structural deviations were classified as:
Malformations: rare and/or probably lethal e.g. hydrocephaly.
Variations: changes which regularly occur also in control groups and which are not of functional significance.

Statistics:

For body weight, body weight gain, food consumption, and mean foetal weight (overall, males, females) the analysis of variance was performed with one factor TREATMENT followed by the Newman-Keuls test for multiple group comparison. Number of corpora lutea, number of implantation, number of foetuses, preimplantation loss, post-implantation loss, and proportion of male foetuses were statistically analysed using the Kruskal-Wallis-test.
In case of suspected significance (probability > chi square < 0.05), the four groups were compared two by two using the Wilcoxon two-sample test (normal approximation - with continuity correction of 0.5).
All significances found (at least p < 0.05) are indicated in the respective tables.
The statistical evaluation was performed with the standard software package SAS release 6.02.

Indices:

pregnancy indices
pre-implantation loss
post-implantation loss
sex ratio

Historical control data:

Historical control data is included in the report.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes. Remark: reduced body weight gain

Details on maternal toxic effects:
There were no behavioural changes and no clinical observations in any animal of all groups. At necropsy unilateral dilatation of the renal pelvis was found in one female of group 3 (150 mg/kg) and two females of group 4 (300 mg/kg). The nature of these findings is considered not to be treatment-related.
In group 4 (300 mg/kg) body weight gain during gestation, particularly during late gestation, was slightly reduced (16 per cent less than the control group from day 10 to 15 post-coitum and 8 per cent less from day 15 to 20 post-coitum) but the difference in comparison with the control group was not statistically significant. This reduced body weight gain is considered to be related to treatment with the test item.
Body weight gain of groups 2 (50 mg/kg) and 3 (150 mg/kg) was comparable with the concurrent control group. Mean daily food consumption was slightly lower in group 4 (300 mg/kg) than in the control group, particularly during treatment. This might be a slightly toxic effect of treatment

Effect levels (maternal animals)

1

Dose descriptor:

NOEL

Effect level:

>= 300 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

2

Dose descriptor:

NOEL

Effect level:

150 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Details on embryotoxic / teratogenic effects:
The mean number of foetuses per dam was slightly lower in group 4 (300 mg/kg). This finding is considered to be related with the slightly reduced mean number of implantations per female and not considered to treatment-related. The mean number of foetuses per dam in groups 2 (50 mg/kg) and 3 (150 mg/kg) was comparable with the control group. Sex distribution of foetuses did not reveal any compound-related effect. Mean foetal weight was slightly increased in group 4 (300 mg/kg). Differences to the control group were statistically significant. This finding must be considered in relation to the reduced mean number of foetuses per female in the highest dose group and not in relation to treatment.
Mean foetal weights of groups 2 (50 mg/kg) and 3 (150 mg/kg) were comparable with the control group.


An external malformation as micrognathia was found in one foetus of group 2 (50 mg/kg). A further foetus in a second litter of the same dose group showed bilateral anophthalmia.
In group 3 (150 mg/kg), one foetus with apodia was observed. Skeletal malformations were not detected.
In group 4 (300 mg/kg) as well as in the control group no malformations were found.
The incidence of skeletal variations did not reveal any treatment-related effects.

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Pre-implantation loss was high in the control group and in group 4 (300 mg/kg). As pre-implantation loss of group 4 (300 mg/kg) was only slightly higher than in the control group (which remains in the upper range obtained from historical background data, this finding is considered to be incidental. In groups 2 (50 mg/kg) and 3 (150 mg/kg) there was no effect of the test item on pre-implantation loss either.

Applicant's summary and conclusion

Conclusions:

In conclusion, administration of the test substance during organogenesis by oral gavage at a dose level of 300 mg/kg elicited slight maternal toxicity (slightly reduced body weight gain and - possibly - slightly reduced food consumption), but no embryotoxicity, and no teratogenicity. Administration of 50 and 150 mg/kg did not elicit any maternal toxicity, embryotoxicity, or teratogenicity.