Potentiation of oxidative cell injury in hepatocytes which have accumulated Ca2+

Incubation of freshly isolated rat hepatocytes with exogenous ATP, but not with succinate, resulted in intracellular Ca2+ accumulation which was partly prevented when the inhibitor of mitochondrial Ca2+ sequestration, ruthenium red, was also present in the medium. Although the bulk of the accumulated Ca2+ was sequestered by the mitochondria, formation of surface blebs and stimulation of phosphorylase alpha activity during incubation of the hepatocytes with ATP indicate that this treatment was also associated with an increase in cytosolic free Ca2+ concentration. When hepatocytes loaded with Ca2+ by preincubation with ATP were exposed to either 2-methyl-1,4-naphthoquinone or t-butyl hydroperoxide, the cytotoxicity of both agents was markedly potentiated. Our results suggest that ATP-induced Ca2+ accumulation in hepatocytes is not due to contamination of the cell suspension with damaged cells or free intracellular organelles and that the intracellular Ca2+ concentration can affect the response to toxic agents.