ROLE OF IRON AND GLUTATHIONE REDOX CYCLE IN ACETAMINOPHEN-INDUCED CYTOTOXICITY TO CULTURED RAT HEPATOCYTES

The aims of this study were to investigate the roles of iron as a cata lyst in reactive oxygen metabolite-mediated cellular injury and of the endogenous antioxidant defenses against acetaminophen-induced cytotox icity in cultured rat hepatocytes. Hepatocytes were isolated and cultu red from either 3-methylcholanthrene-treated or untreated rats. Cytoto xicity was evaluated by measuring Cr-51 and lactate dehydrogenase rele ase. Acetaminophen caused dose-dependent cytotoxicity in 3-methlychola nthrene-treated, but not untreated cells. There was a good correlation between Cr-51 and lactate dehydrogenase release values. Pretreatment with both diethyl maleate, which covalently binds glutathione as catal yzed by glutathione-S-transferase, and bis(chloroethyl)-nitrosourea, a n inhibitor of glutathione reductase, enhanced acetaminophen-induced c ytotoxicity. Inhibition of endogenous catalase activity by pretreatmen t with aminotriazole did not affect acetaminophen-induced cellular dam age. Addition of exogenous catalase failed to protect against acetamin ophen-induced cytotoxicity. Preincubation with both deferoxamine, a fe rric iron chelator, and phenanthroline, a ferrous iron chelator, dimin ished acetaminophen-induced cytotoxicity. These results indicate that iron is crucial in mediating acetaminophen-induced cytotoxicity and th at the glutathione redox cycle, but not catalase, plays a critical rol e in the endogenous defenses against acetaminophen-induced cellular da mage in cultured rat hepatocytes in vitro.