Influence of misonidazole on survival of wild-type and radiosensitive mutants of yeast.

Survival curves were obtained for haploid and diploid yeasts, Saccharomyces cerevisiae, of a wild-type strain and radiosensitive mutants exposed to gamma-rays in oxygenated and hypoxic conditions both in the absence and in the presence of misonidazole. Misonidazole enhanced the radiosensitivity only of hypoxic cells. A correlation between oxygen and misonidazole sensitization was observed. The data confirm that misonidazole mimics the sensitizing effect of oxygen. The degree of liquid-holding recovery of yeast cells was greater when the cells were irradiated in hypoxic conditions with than without misonidazole. Possible reasons for the observed radiation responses are discussed.