Effect of vitamin E on survival, glutathione reductase and formation of chromium (V) in Chinese hamster V-79 cells treated with sodium chromate (VI).
The effect of vitamin E on cytotoxicity induced by Na2CrO4 was evaluated by colony-forming assay using Chinese hamster V-79 cells. Pre-treatment with alpha-tocopherol succinate (vitamin E) for 24 h prior to exposure to Na2CrO4 resulted in a marked decrease in the cytotoxicity caused by this compound. The reduction of chromate-induced cytotoxicity was observed at all concentrations of Na2CrO4 (5-15 microM), and the protective effect increased with higher concentrations of vitamin E (5-25 microM). The level of glutathione reductase activity, which is capable of reducing chromate, was not affected by cellular pre-treatment with vitamin E. However, Na2CrO4 decreased glutathione reductase activity in a concentration-dependent fashion (5-15 microM) and pretreatment with vitamin E resulted in a significant recovery of enzyme activity suppressed by Na2CrO4, suggesting that this enzyme inhibition is linked to the cytotoxicity of this metal. Electron spin resonance studies showed that a paramagnetic chromium (V) complex was formed in cells treated with Na2CrO4, and that cellular pre-treatment with vitamin E reduced the formation of this chromium (V) intermediate. These results indicate that vitamin E protects cells from chromate-induced cytotoxicity as well as from enzyme inhibition, and also suggest that Na2CrO4-induced cytotoxicity is mediated by the generation of a reactive intermediate.
Sugiyama
M
M
Department of Medical Biochemistry, Kurume University School of Medicine, Japan.
Ando
A
A
Ogura
R
R
D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002840:Chromates / Q000378:metabolism* / Q000633:toxicity*; D006224:Cricetinae; D003412:Cricetulus; D005980:Glutathione Reductase / Q000378:metabolism*; D017670:Sodium Compounds; D014810:Vitamin E / Q000494:pharmacology*
D002840:Chromates; D017670:Sodium Compounds; D014810:Vitamin E; C028982:sodium chromate(VI); D005980:Glutathione Reductase