Comparison of the peripheral blood micronucleus test using flow cytometry in rat and mouse exposed to aneugens after single-dose applications.

Detection of clastogenic compounds in the peripheral blood micronucleus test (MNT) in rats is a well-established methodology. However, the results obtained on the induction of micronuclei by aneugens in rat peripheral blood are controversial. Our aim was a comparative evaluation of the peripheral blood flow cytometry MNT in Wistar Han rat and CD1 mouse exposed to three aneugens (vinblastine, vincristine and colchicine) after single-dose applications. In addition, the same compounds were tested in the rat bone marrow MNT. The treatment with vinblastine (0.25, 0.5, 1, mg/kg), vincristine (0.025, 0.05, 0.1 mg/kg) or colchicine (0.7, 1, 1.3 mg/kg) induced no statistically significant increase in MN-PCEs (micronucleated polychromatic erythrocytes or reticulocytes) in rat peripheral blood. In rat bone marrow, a clear statistically significant increase in MN-PCE was found with vincristine and vinblastine. However, colchicine showed a clear increase in MN-PCE frequency without reaching statistically significant level only at 1 mg/kg. The positive effect in the bone marrow MNT shows that the target organ was exposed to the appropriate concentration levels of the respective aneugens. In mouse, the peripheral blood flow cytometry analysis after the treatment with vinblastine, vincristine and colchicine showed clear statistically significant increase in MN-PCE with all three compounds. The experiments with splenectomized rats treated with vincristine and colchicine were performed and statistically significant increases in MN-PCE were found with 0.05, 0.1, 0.15 mg/kg of vincristine and 0.7 and 1 mg/kg of colchicine. Our results demonstrate that micronucleated cells induced by aneugens are removed from rat peripheral blood by the spleen due to the large size of micronuclei. Based on our data, it is concluded that the flow cytometry peripheral blood MNT after single-dose applications is an appropriate test system for evaluating the genotoxic effects of aneugens in mice. However, in rats peripheral blood MNT aneugen detection might require multiple-dose applications to overwhelm the spleen effect.