Addition of silver nitrate or silver lactate to freshly isolated hepatocytes caused dose-dependent loss of cell viability, measured by trypan blue exclusion, at concentrations within 30-70 microM. Silver cytotoxicity was accompanied by a decrease in hepatic thiol concentration and an increase in lipid peroxidation. Treatment of hepatocytes with the reduced glutathione (GSH)-depleting agent diethylmaleate markedly increased their vulnerability to silver toxicity whereas protective effects were produced by the thiol-reducing agent, dithiothreitol. Both alpha-tocopherol, which protected from the onset of silver-associated lipid peroxidation, and the iron chelator agent, deferoxamine failed to prevent loss of cell viability. These data suggest that perturbation of intracellular thiol homeostasis may play a critical role in the mechanism underlying silver-induced lethal damage to isolated rat hepatocytes.