The role of glutathione reductase in the cytotoxicity of chromium (VI) in isolated rat hepatocytes.
Chromium (VI) is an environmental and occupational carcinogen, and it is accepted that intracellular reduction is necessary for DNA damage and cytotoxicity. We have investigated the interaction of Cr(VI) with hepatocytes in vitro to determine the contribution of various hepatic enzymes to the reduction of Cr(VI). Cr(VI) caused a dose-dependent decrease in cell viability and intracellular reduced glutathione (GSH) levels between 100 and 500 microM within 3 h exposure of hepatocytes. Both DT-diaphorase and cytochrome P450 play only a minor role in detoxifying Cr(VI) and/or its metabolites. (GSH) appears to act as a non-enzymatic reductant, reducing Cr(VI) to a toxic form. The evidence for this is two-fold. Firstly, GSH was depleted during the metabolism of Cr(VI) and, secondly, pretreatment of the cells with diethylmaleate to deplete GSH levels, partially protected the cells from Cr(VI) toxicity. Glutathione reductase appears to play an important role in the enzymatic reduction of Cr(VI) as inhibition of this enzyme by carmustine (BCNU) markedly protected the cells from cytotoxicity.
Gunaratnam
M
M
Bioengineering Unit, Strathclyde University, Wolfson Centre, 106 Rottenrow, G4 0NW, Glasgow, UK.
Grant
M H
MH
D000818:Animals; D002330:Carmustine / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002857:Chromium / Q000633:toxicity*; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D001728:Dicumarol / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D005980:Glutathione Reductase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D066298:In Vitro Techniques; D008297:Male; D008797:Metyrapone / Q000494:pharmacology; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000037:antagonists & inhibitors / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D017207:Rats, Sprague-Dawley
D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D002857:Chromium; D001728:Dicumarol; D003577:Cytochrome P-450 Enzyme System; D016660:NAD(P)H Dehydrogenase (Quinone); D005980:Glutathione Reductase; D005978:Glutathione; D002330:Carmustine; D008797:Metyrapone