A comparison of the incidence of micronuclei in blood and bone marrow in 3 strains of mouse dosed with cyclophosphamide or hexamethylphosphoramide (HMPA).

The response of 3 strains of mouse (C57Bl/6J, C3H/C57 hybrid and BALBC/CBA) to cyclophosphamide (75 mg/kg) and hexamethylphosphoramide (HMPA) (1.28 ml/kg) were compared in the micronucleus test. Each compound was administered by intraperitoneal injection on two consecutive days and samples of bone marrow and blood taken for examination at 48 and 72 h after the first injection. Both test chemicals produced a statistically significant increase (P 0.001) in the incidence of micronuclei in bone marrow cells in all strains at both sampling times but the response with HMPA in C57Bl/6J mice appears to occur earlier than in the other two strains. Significant increases in micronuclei were seen in circulating erythrocytes only at 48 h in C57Bl/6J mice with both test chemicals and in C3H/C57 mice only with cyclophosphamide.