Chemical Protection of Bacteria and Cultured Mammalian Cells by Sulfur-Containing Compounds

Protection by sulfur-containing compounds was studied with use of bacteria E. coli BH and cultured mouse leukemic cells, L 5178 Y, and the protective mechanisms were discussed. The dose reduction factors of non-sulfhydryl compounds observed in the bacteria were the same as those observed in the mammalian cells, and the protective activity of these compounds was proportional to their reaction rates with hydroxyl radicals. On the other hand, sulfhydryl compounds except glutathione, offered much greater protection than the protection which was anticipated from their radical scavenging activiy. From studies under anoxia, the protection of cysteine was explained by its OH scavenging and competition with oxygen. For MEA, protection against the direct action of radiation was suggested, in addition. This was supporrted by the significant protection in the frozen state.