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.

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.

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