Differential cytotoxicity of sodium arsenite in human fibroblasts and Chinese hamster ovary cells.

Human skin fibroblast (HF) cells were approximately 10-fold more sensitive to sodium arsenite toxicity than Chinese hamster ovary (CHO) cells using the clonogenic assay. G1-phase CHO cells showed a 2-fold increase in the susceptibility to the toxic effects of sodium arsenite as compared to asynchronous CHO cells. The concentrations of sodium arsenite required to kill 50% of the cell population were correlated with the intracellular glutathione levels in asynchronous, G1-phase CHO, and asynchronous HF cells. Moreover, verapamil potentiated the cytotoxicity of sodium arsenite in CHO cells but not in HF cells. These results indicated that a verapamil-sensitive outward channel may be involved in detoxification of arsenic in CHO cells. Treatment with sodium arsenite resulted in a marked cell-cycle disturbance in CHO, but not in HF cells. Thus, CHO cells may take time to recover from sodium arsenite insult before progressing through the cell cycle. A different response of sodium arsenite in heat-shock protein synthesis in these 2 cell types was also revealed.