Modification of radiation-induced chromosome damage and micronucleus induction in mouse bone marrow by misonidazole and hyperthermia.

The effect of misonidazole (MISO), local hyperthermia (HT) and their combination on radiation-induced chromosome damage and micronucleus (MN) induction was studied in mouse bone marrow cells. It was found that MISO treatment did not enhance the clastogenic effect of radiation, which indicates a lack of radiosensitization of bone marrow chromosomes. But post-irradiation HT increased the frequency of aberrant cells and MN. A combination of MISO and HT produced a significant increase in the frequency of radiation-induced aberrant cells and MN at all the radiation doses as compared to radiation alone. The percentage of aberrant cells as well as the percentage of MN showed a linear quadratic increase with radiation dose in all the treatment groups. At higher radiation doses, cells with > 1 MN increased quadratically with a pronounced increase in cells bearing > 2 MN and severely damaged cells (SDCs) at radiation doses above 3.0 Gy in the HT and MISO+HT treated groups. Our results indicate that though MISO itself may not have a radiosensitizing effect on mouse chromosomes, a combination of MISO with HT can enhance the radiation damage in normal bone marrow.