Toxicity studies in isolated hepatocytes from selenium-deficient rats and vitamin E-deficient rats.

Isolated hepatocytes from selenium-deficient, vitamin E-deficient, and control rats were treated with cumene hydroperoxide (CuOOH), phorone (diisopropylene acetone), acetaminophen, and diquat. The effect of these chemicals on cell viability, glutathione synthesis and release, and lipid peroxidation as measured by thiobarbituric acid (TBA)-reactive substances was determined during a 4-hr incubation in a complete medium under 95% O2:5% CO2 at 37 degrees C. CuOOH-treated (0.5 mM) selenium-deficient and vitamin E-deficient hepatocytes lost viability sooner than control hepatocytes. Thus, loss of selenium or vitamin E from the hepatocyte resulted in a cell more susceptible to damage by CuOOH. Phorone treatment (1.65 mM) resulted in depletion of intracellular glutathione in all three groups to approximately 20% of that in untreated hepatocytes. Cell viability and TBA-reactive substances were the same in treated and untreated hepatocytes. Thus, lowering of intracellular glutathione did not result in the spontaneous loss of cell viability or increased lipid peroxidation in selenium-deficient or in vitamin E-deficient hepatocytes. Acetaminophen appeared to be less toxic to selenium-deficient hepatocytes than to controls. This finding is in agreement with whole animal studies reported previously showing that selenium deficiency protects rats against acetaminophen hepatotoxicity. A potential explanation of this result is stimulation of glutathione synthesis by selenium deficiency. Severely vitamin E-deficient hepatocytes were protected from cell death by 12.5 and 25.0 mM acetaminophen, apparently by its antioxidant properties, while 50.0 mM acetaminophen was toxic to them. At all concentrations used, acetaminophen decreased the TBA-reactive substances present in the hepatocyte suspensions. Diquat (0.1 mM) caused more rapid cell death and higher levels of TBA-reactive substances in selenium-deficient hepatocytes than in control hepatocytes. Diquat toxicity in selenium-deficient isolated hepatocytes was not as severe as its toxicity in selenium-deficient whole animals, however.