Registration Dossier

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:
23 June 2004 and 25 April 2005.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP-compliant guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2005
Report date:
2005

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)
Qualifier:
according to guideline
Guideline:
other: Japanese Ministry of Agriculture, Forestry and Fisheries Testing Guidelines for Toxicology Studies, 12 NohSan No 8147,24 November 2000
GLP compliance:
yes
Limit test:
yes

Test material

Constituent 1
Reference substance name:
1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione
EC Number:
248-597-9
EC Name:
1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione
Cas Number:
27676-62-6
IUPAC Name:
1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazinane-2,4,6-trione
Details on test material:
- Physical state: white powder
- Storage condition of test material: 4°C in the dark

Test animals

Species:
rat
Strain:
other: Sprague-Dawley Crl:CD® (SD) BR
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River (UK) Limited, Margate, Kent
- Age at study initiation: ten to twelve weeks
- Weight at study initiation: 182 to 287g
- Housing: individually in solid-floor polypropylene cages with stainless steel lids furnished with softwood flakes (Datesand Ltd., Cheshire, UK)
- Diet: Rodent PMI 5002 (Certified) Diet, BCM IPS Ltd, London, UK (ad libitum)
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ± 2
- Humidity (%): 55 ± 15
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
arachis oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
For the purpose of this study the test material was prepared at the appropriate concentrations as a suspension in Arachis oil BP

VEHICLE
- Amount of vehicle (if gavage): 4 ml/kg
- Concentration in vehicle: 0, 25, 75, 250 mg/ml
- Lot/batch no. (if required):
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The stability and homogeneity of the test material formulations were previously determined by Safepharm Analytical Laboratory (SPL Project number 1976/001) and show those formulations to be stable for at least fourteen days. Formulations were therefore prepared weekly and stored at approximately +4°C in the dark.
Samples were taken of each test material formulation and were analysed for concentration of the test article at Safepharm Analytical Laboratory. The results indicate that the prepared formulations were within ± 4 % of the nominal concentration.
Duration of treatment / exposure:
from day 5 to 19 of gestation
Frequency of treatment:
daily
Duration of test:
Animals were killed on day 20 of gestation.
Doses / concentrations
Remarks:
Doses / Concentrations:
100, 300, 1000 mg/kg bw
Basis:
actual ingested
No. of animals per sex per dose:
24
Control animals:
yes, concurrent vehicle

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: immediately before dosing and one and five hours after dosing during the working week of the treatment period (excluding the study Day on the 19/08/2004 and 23/08/2004 due to technician error). Animals were observed immediately before dosing and one hour after dosing at weekends and public holidays.

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: Individual bodyweights were recorded on Day 3 (before the start of treatment) and on Days 5, 6, 7, 8, 11, 14 and 17. Bodyweights were also recorded at terminal kill (Day 20).

FOOD CONSUMPTION: Yes
- Food consumption was recorded for each individual animal at Day 3, 5, 8,11,14,17 and 20.

POST-MORTEM EXAMINATIONS: Yes / No / No data
All animals were killed by carbon dioxide asphyxiation followed by cervical dislocation on Day 20 of gestation. All animals were subjected to a full external and internal examination and any macroscopic abnormalities were recorded.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
The ovaries and uteri of pregnant females were removed, examined and the following data recorded:
i) Gravid uterus weight
ii) Number of corpora lutea
iii) Number, position and type of intrauterine implantation
iv) Foetal sex
v) External foetal appearance
vi) Foetal weight
vii) Placental weight
The uteri of any apparently non-pregnant females were immersed in 10% aminosulnphide to reveal evidence of implantation.
Implantation types were divided into:
Early Death: No visible distinction between placental/decidual tissue and embryonic tissue
Late Death: Separate embryonic/foetal and placental tissue visible
Dead Foetus: A foetus that had died shortly before necropsy. These were included as late deaths for reporting purposes
All implantations and viable foetuses were numbered according to their intrauterine position.
Fetal examinations:
The foetuses were killed by subcutaneous injection of sodium pentobarbitone. Alternate foetuses were identified using an indelible marker and placed in Bouin's fixative. Foetuses were transferred to 90% industrial methylated spirits (IMS) in distilled water and examined for visceral anomalies under a low power binocular microscope. The remaining foetuses were identified using colour coded wires and placed in 70% IMS in distilled water. The foetuses were eviscerated, processed and the skeletons stained with alizqarin red. The foetuses were examined for skeletal development and anomalies.
Statistics:
The following parameters were analysed statistically, where appropriate using the test methods outlined below:
Female bodyweight change and food consumption: Bartlett's test for homogeneity of variance and one way analysis of variance; followed by Dunnetts multiple comparision test; or if unequal variances were observed, an alternative multiple comparision test was performed. All caesarian necropsy parameters and foetal parameters: Kruskal-Wallis non-parametric analysis of variance; and a subsequent pairwise analysis of control values against treated values using the Mann-Whitney 'U' test, where significance was seen.
Foetal evaluation parameters, including skeletal or visceral findings: Kruskal-Wallis nonparametric analysis of variance and Mann-Whitney 'U' test.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:no effects

Details on maternal toxic effects:
Mortality:
There were no unscheduled deaths.

Clinical Observations:
No clinically observable signs of toxicity were detected in test or control animals throughout the study period. One female treated with 100 mg/kg/day showed generalised fur loss on Day 20 only. This was incidental and of no toxicological importance.

Bodyweight:
No adverse effect on bodyweight development was detected. Females treated with 1000 mg/kg/day showed a statistically significant increase in bodyweight gain between Days 3 and 5 of gestation. The dose response was unconvincing and this minimal (p<0.05) increase in bodyweight gain is unlikely to be associated with test material toxicity.

Food Consumption:
No adverse effect on dietary intake was detected. Statistical analysis of the data revealed no significant intergroup differences.

Post Mortem Studies:
No treatment-related macroscopic abnormalities were detected in females at terminal kill. Females treated with 300 or 100 mg/kg/day showed a statistically significant reduction in the total percent of foetuses showing external findings. The intergroup differences were considered to be due to low incident findings being detected in control animals and was considered unrelated to treatment.

Effect levels (maternal animals)

open allclose all
Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Details on embryotoxic / teratogenic effects:
Uterine Implantation Data:
No treatment-related effects were detected upon any of the uterine parameters examined. The number of pregnant females from each dose group were sufficient to allow full evaluation to be performed. Females treated with 100 mg/kg/day showed a statistically significant increase in pre-implantation losses. In the absence of a dose-related response, the intergroup difference was considered to be without toxicological importance.

Foetal Data
No treatment-related effects were detected upon foetal viability, growth and development. For all dose groups, there were no significant treatment-related trends in the proportion of foetuses (or litters) with evidence of visceral or skeletal anomalies. The type of visceral and skeletal anomalies were those commonly observed for this type of study. Females treated with 100 mg/kg/day showed a statistically significant reduction in the percent of foetuses showing one thoracic vertibral centra semi-bipartite. In the absence of a dose-related response, the intergroup difference was considered to be without toxicological importance.

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

Females from all treatment groups showed a statistically significant increase in the number of foetuses showing seven or more ossified post lumbar vertebral centra. Consequently the number of foetuses showing less than seven ossified post lumbar vertebral centra was lower for all treatment groups. The expected number of ossified post lumbar vertebral centra is seven thus indicating a higher incidence of foetuses with expected or above expected degrees of ossification. The dose-related response was unconvincing and all group mean percentages were within historical ranges for rats of the strain and age used; as such intergroup difference was considered to be without toxicological importance.

Females from all treatment groups showed a statistically significant reduction in the number of foetuses showing two or more ossified phalanges and consequently an increase in the number of foetuses showing less than two ossified phalanges. Ossification of phalanges in Day 20 foetuses is regarded as precocious ossification and therefore represents an unexpected degree of foetal development. It is considered that a treatment-related effect on precocious ossification is not representative of a developmental toxic event as there is no concomitant effect upon what is regarded as normal ossification (or other limb bones). The dose-related response was unconvincing and since it was control values which had the higher incidence of precocious ossification the intergroup differences were not considered evidence of a treatment-related effect.

Females treated with 1000 and 300 mg/kg/day showed a statistically significant increase in the number of foetuses showing greater than six ossified metatarsals. The standard number of ossified metatarsals in Day 20 foetuses is greater than six, therefore, the intergroup differences indicate a higher number of foetuses showing a normal number of ossified metatarsals compared to control and as such, is considered of no toxicological importance.

Females from all treatment groups showed a statistically significant increase in the number of foetuses showing a medium fontanelle, and subsequently a reduction in the number of foetuses showing a small fontanelle. The standard classification of fontanelle size is medium and therefore the intergroup differences were considered to be attributable to the increased number of control foetuses showing a small fontanelle, of which the values were outside historical ranges for rats of the strain and age used, and as such, were considered of no toxicological significance.

Applicant's summary and conclusion

Conclusions:
NOAEL Maternal toxicity 1000 mg/kg bw/day (actual dose received)
NOAEL Devleopmental toxicity 1000 mg/kg bw/day (actual dose received)