2,5-di-tert-pentylhydroquinone

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / bone marrow chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

October 13- December 21, 1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study is performed according to the applicable OECD and EPA guidelines under GLP conditions. No deviations were reported.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1988

Report date:

1988

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5385 (In Vivo Mammalian Cytogenetics Tests: Bone Marrow Chromosomal Analysis)

Deviations:

no

GLP compliance:

yes

Type of assay:

chromosome aberration assay

Test material

Test material information

Constituent 1

Details on test material:

- Name of test material (as cited in study report): Santovar A
- Substance type: white powder
- Physical state: solid
- Analytical purity: responsibility of sponsor
- Storage condition of test material: room temperature

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Massachusetts
- Age at study initiation: 6.5 weeks
- Weight at study initiation: males: 163 - 200 g; females: 126 - 153 g.
- Assigned to test groups randomly: yes
- Fasting period before study: 18 hours
- Housing: individually in stainless, steel cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 3 days

Administration / exposure

Route of administration:

oral: unspecified

Vehicle:

- Vehicle(s)/solvent(s) used: corn oil

Duration of treatment / exposure:

6, 18, 30 hours

Frequency of treatment:

single dose

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 1000 mg/kg
Basis:
actual ingested

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Positive control(s):

- Cyclophosphamide
- Route of administration: oral gavage
- Doses / concentrations: 50 mg/kg bw

Examinations

Tissues and cell types examined:

bone marrow

Details of tissue and slide preparation:

DETAILS OF SLIDE PREPARATION:
Cells were resuspended in a small amount of freshly prepared fixative. Slides were prepared by dropping the cell suspension on precleaned methanol-wet glass slides followed by flaming. Slides were stained in 3% Giemsa in distilled water for 10 minutes, rinsed in distilled water and air dried. Slides were cleared in xylene and coverslips mounted with Permount.

Evaluation criteria:

Cytogenetic abnormalities were classified on a standard scoring sheet according to chromosome or chromatid aberrations and further according to type of aberration. Aberrations were classified according to the nomenclature of Buckton and Evans, 1973 and Savage, 1975.

Statistics:

Mean number of aberrations per cell per rat (50 cells per rat) were analyzed for statistically significant increases in chromosome aberration by a one way analysis of variance (ANOVA). Each sampling time was analyzed separately as compared to its concurrent vehicle control group. The mean and standard deviation of aberratlons/cell were also determlned for each group of rats (500 cells: 50 cells per rat). The number of aberrant metaphases was analyzed by Chi-square analysis for statistically significant increases. Vehicle control groups were also analyzed by a one way ANOVA for time related differences in aberrations, as were the three groups of rats administered Santovar A. Statistical signlficance was determined at the p<= 0.05 probabillty level.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

RESULTS OF RANGE-FINDING STUDY
- Dose range: rats expressed toxicity signs at 950 mg/kg bw, 1000 mg/kg bw was chosen for definitive study

RESULTS OF DEFINITIVE STUDY
- Types of structural aberrations for significant dose levels (for Cytogenetic or SCE assay): no structural chromosomal aberrations induced by testing substance
- Appropriateness of dose levels and route: all rats dosed with 1000 mg/kg exhibited mild to severe toxicity signs at all times evaluated and 2 females at 18 hours testing group died. Thus, the tested substance was dosed near the maximum tolerated dose.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
Male and female Fisher 344 rats received 0 and 1000 mg/kg Santovar A by oral gavage. The hemopoietic cells of the bone marrow were analyzed after 6, 18, and 30 hours. No statistically significant increases in the incidence of aberrations or in the number of cells with one or more aberrations were observed in animals treated with Santovar A at 1000 mg/kg at any of the three sampling times evaluated. Therefore, under the conditions of this assay, Santovar A was not clastogenic to the hemopoietic cells of the rat bone marrow.

Executive summary:

This study was designed to evaluate the potential of Santovar A to induce structural chromosomal aberrations in the hemopoietic cells of the rat bone marrow when administered by oral gavage. Based on a preliminary study in which Santovar A was evaluated at 950 mg/kg, a dose of 1000 mg/kg of body weight was selected for evaluation at the 6, 18 and 30 hour sacrifice intervals. Vehicle control nice administered corn oil were included at each sampling time. The positive control, cyclophosphamide (CP) at 50 mg/kg was included at the 18 hour sampling time. Santovar A was administered in single oral doses to three groups of fasted young adult Sprague Dawley rats. Approximately two hours prior to each sacrifice time, animals were administered colchicine at 4 mg/kg of body weight to arrest cells in metaphase. At the appropriate time, animals were sacrificed and both femurs were removed from each animal ad metaphase slides prepared. Slides were stained, coded and scored for chromosomal aberrations.

All rats dose with Santovar A (1000 mg/kg) exhibited from mild to severe pharmacotoxic signs. In addition, to females from the 18 hours harvest group died. These results suggest that Santovar A was tested at or near the maximum tolerated dose.

A total of 50 metaphase cells were analysed for each animal (when possible) for the presence of chromatid and chromosome type aberrations. Aberrations were classified according to type on a standard scoring sheet and the number of aberrations in each cell tabulated. The number of centromeres in each cell was counted and recorded.

Data was evaluated for statistically significant increases in aberrations per cell in treatment groups as compared to the vehicle control groups. The proportion of aberrant metaphases was also evaluated for statistically significant increases over the vehicle control groups. Data were evaluated separately for each harvest interval.

The positive control article, CP, resulted in significant increases in the incidence of chromosome aberrations and in the proportion of metaphases with one or more aberrations.

No statistically significant increase in the incidence of aberrations or in the number of cells with one or more aberrations were observed in animals treated with Santovar A (1000 mg/kg) at any of the three sampling times evaluated. Therefore, under the conditions of this assay, Santovar A was not clastogenic to the hemopoietic cells of the rat bone marrow.