Modification of radioresponse of sublethally irradiated mouse jejunum by misonidazole

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.

Dose-dependent increase in the frequency of micronuclei and chromosomal aberrations by misonidazole in mouse bone marrow

Cytogenetic effects produced in bone marrow of mice by various doses of misonidazole (MISO, 100 to 1000 mg/kg bodyweight) were studied by assaying the induction of micronuclei (MN) and chromosomal aberrations. Misonidazole increased the frequency of both micronuclei and chromosomal aberrations over normal at 24 h after treatment, however, the values were statistically significant from normal only at drug doses above 250 mg/kg. The increase was proportional to the drug dose with a best fit to linear quadratic model for MN induction. For chromosomal aberrations the data fitted equally well to linear as well as linear quadratic models.