Treatment of mice with a novel antineoplastic agent taxol before irradiation increases the frequency of micronuclei in the bone marrow.

The frequency of micronucleated polychromatic erythrocytes (MPCE) and the normochromatic erythrocytes (MNCE) and polychromatic and normochromatic erythrocyte ratio (P/N ratio) was studied at 12, 24 and 36 h postirradiation in the bone marrow of male mice treated or not with taxol before exposure to 0-4 Gy of 60Co gamma radiation. The frequency of MPCE increased with the increase in radiation dose in a dose-related manner in the irradiated control group. A peak frequency of MPCE was observed at 24 h postirradiation in irradiated control group. The pattern of increase in MNCE was similar to that of MPCE except that a highest number of MNCE was scored at 36 h postirradiation. Taxol administration to animals before irradiation resulted in a significant elevation in the frequency of MPCE and MNCE at all the postirradiation time periods studied. This increase was dose related as observed in the irradiated control group. Irradiation resulted in a dose-dependent decline in the P/N ratio at all the postirradiation time periods studied. The P/N ratio was significantly lower in the taxol + irradiated group compared to the irradiated control group at all postirradiation time periods. A maximum decline in P/N ratio was observed at 36 h postirradiation for both irradiated control and taxol + irradiated groups. The dose response for MPCE, MNCE and P/N ratio was linear quadratic for both the irradiated and taxol + irradiated groups.