Thymidine

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: gene mutation

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: See read-across justification attached.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

2007

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Deviations:

no

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Test material form:

solid: crystalline

Details on test material:

- Name of test material: L-Thymidine

Test animals

Species:

mouse

Strain:

CD-1

Sex:

male/female

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

- Vehicle(s)/solvent(s) used: Dimethylsulfoxide (DMSO)

Duration of treatment / exposure:

Single treatment

Post exposure period:

Bone marrow preparations obtained 24 and 48 hours postdose were assessed.

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 500, 1000, 2000 mg/kg bw
Basis:
nominal conc.

No. of animals per sex per dose:

Each treated and control group must include at least 5 analysable animals per sex.

Control animals:

yes

Positive control(s):

Appropriate positive controls were used.

Examinations

Tissues and cell types examined:

Bone marrow preparations.

Evaluation criteria:

There are several criteria for determining a positive result, such as a dose-related increase in the number of micronucleated cells or a clear increase in the number of micronucleated cells in a single dose group at a single sampling time. Biological relevance of the results should be considered first. Statistical methods may be used as an aid in evaluating the test results. Statistical significance should not be the only determining factor for a positive response. Equivocal results should be clarified by further testing preferably using a modification of experimental conditions.
A test substance for which the results do not meet the above criteria is considered nonmutagenic in this test.

Results and discussion

Test results

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
No evidence of chromosome damage occurred in this in vivo micronucleus test.

Executive summary:

A study was carried out according to OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test). This in vivo micronucleus test was performed in CD-1 mice given single oral doses of 0, 500, 1000, or 2000 mg/kg bw (limit dose). The numbers of micronuclei in bone marrow preparations obtained at 24 and 48 h postdose were determined. The test item was prepared as a solution in DMSO and appropriate negative and positive controls were used. No evidence of chromosome damage occurred in this mouse micronucleus test following single oral doses up to 2000 mg/kg bw.