Evaluation of the general suitability of the rat for the micronucleus assay: the effect of cyclophosphamide in 14 strains

Abstract To evaluate the general suitability of the rat for the micronucleus assay, we conducted the assay in males of 14 different strains, 13 inbred (ACI, BN, BUF, COP, DRH, F344, IS, LEW, RCS, SHR, WAG, WKYO, WTC) and 1 outbred (SD), using cyclophosphamide as the test chemical. Cyclophosphamide at 0 (vehicle), 5, 10, or 20 mg/kg per day was administered orally twice, 24 h apart, to five rats per dosage group. Bone marrow and peripheral blood were collected 24 h after the second treatment. All 14 strains showed a positive response to cyclophosphamide, with slight differences in sensitivity. We concluded that the rat is suitable for the micronucleus assay regardless of strain.