Effects of sodium arsenite on the cytotoxicity of bleomycin

Our present data show that posttreatment with sodium arsenite has no effect on the cytotoxicity of bleomycin (BLM), a radiomimetic agent, in Chinese hamster ovary (CHO) cells, human skin fibroblasts, and HeLa cells. However, pretreatment with sodium arsenite potentiated the cytotoxic effects of BLM in CHO cells. This effect decreased with increasing time interval between the treatments with sodium arsenite and BLM. BLM-inactivating activity was markedly reduced in cells pretreated with sodium arsenite. Furthermore, both arsenite-potentiated BLM cytotoxicity and arsenite-reduced BLM-inactivating activity were abolished by cycloheximide. These results suggest that the potentiation effect of sodium arsenite on BLM cytotoxicity may be due to the decrease of BLM-inactivating activity. In addition, only a slight increase in G2 phase population and no apparent change in intracellular glutathione levels were observed in CHO cells pretreated with sodium arsenite.