human fibroblasts ( hfw ) were 10-fold more susceptible than chinese hamster ovary ( cho - k1 ) cells to sodium arsenite . 
 comparison of cellular antioxidant enzyme activities showed that cho - k1 cells contained 3- and 8-fold more glutathione - peroxidase and catalase activities , respectively , than hfw cells . 
 since vitamin e , methylamine , and benzyl alcohol could prevent , in part , the arsenite - induced killing of hfw cells , we suggest that arsenite can induce oxidative damage in hfw cells . 
 we have also established arsenic - resistant cells , sa7 and cl3r , from cho cells and from a human lung adenocarcinoma cell line ( cl3 ) , respectively . 
 the arsenic resistance of sa7 cells was attributed mainly to elevation of glutathione s - transferase pi levels , and that of cl3r cells was possibly due to an increase in heme oxygenase activity . since 
 induction of heme oxygenase is a general response to oxidative stress , we suspect that the differential toxicity of arsenic to human and animal cells could be due to arsenic 's more efficient induction of oxidative damage in human cells.imagesfigure 5.figure 6 .