Radioprotecting action of chemical compounds on gamma-irradiated yeast cells of various genotypes.

The radioprotective efficiency of cysteamine and cysteine has been studied on haploid and diploid, Saccharomyces cerevisiae, wild-type and various X-ray repair deficient rad mutants. The correlation between the radioprotecting action of cysteamine and cell repair capacity was demonstrated for diploid yeasts; such a correlation was not expressed for wild-type and rad mutant haploid yeast cells. It was concluded that the radioprotective action may involve cellular recovery processes, which may be mediated by a recombination-like mechanism, for which the diploid state is required. Liquid holding recovery was shown not to participate in radioprotection, judged by the absence of the influence of cysteine on the delay of the first postradiation budding as well as by the additive action of cysteine and liquid holding recovery.