Influence of catalase on the radiation sensitizing effect of misonidazole.

The radiation modifying action of misonidazole and catalase was investigated in Bacillus megaterium spores at various oxygen concentrations. Catalase (120 micrograms/ml) decreased the radiation sensitizing action of misonidazole. Misonidazole as an electron affinic radiation sensitizer enhanced the build up of H2O2, thus promoting the reaction with catalase. Protection by catalase was not enough to eliminate the total radiation sensitizing effect of misonidazole.

The effect of superoxide dismutase on the radiosensitivity of bacterial spores at various oxygen concentrations.

Superoxide dismutases are considered to be essential protective agent against radiation injury. Experiments were carried out to investigate the effect of extracellularly added SOD on the radiosensitivity of Bacillus megaterium spores. 120 micrograms/ml SOD had no effect on the radiosensitivity of Bacillus megaterium spores at different oxygen concentrations. Relative enzyme activity obtained at various oxygen concentrations indicating the lack of oxygen effect in the radiation-induced inactivation of SOD.

Combination of misonidazole and lipoic acid on the radiation sensitivity of Bacillus megaterium spores.

The radiation sensitizing action of a combination of misonidazole and lipoic acid was investigated in Bacillus megaterium spores at various oxygen concentrations. Lipoic acid and misonidazole were applied in two concentrations (0.1 and 1.0 mmol/l) and four combinations were prepared from them. No uniform correlation was found, neither to the combination of the compounds nor to the gas conditions. The combination of two radiation sensitizing compounds with in all probability different action mechanisms does not unequivocally enhance the radiation sensitizing effect under anoxic and hypoxic conditions.