The decisive pO2-levels in haloalkane-mediated liver cell injury

The model hepatotoxin carbon tetrachloride (CCl4) was used to study haloalkane free radical-induced lipid peroxidation in isolated rat hepatocytes at steady state oxygen partial pressures (pO2) between 0.2 and 100 mmHg. Equilibrium oxygen conditions were achieved by using an oxystat system. Monitoring of hepatocellular oxygen uptake, malondialdehyde-formation and low-level chemiluminescence during incubations of CCl4-supplemented hepatocytes indicated a drastic stimulation of lipid peroxidation at pO2-levels between 1 and 10 mmHg. Above and below this pO2-region the potency of CCl4 to induce lipid peroxidation sharply decreased. The evaluation of cellular damages by determining trypan blue exclusion and lactate dehydrogenase leakage revealed that in the presence of CCl4 hepatocellular injury was significantly increased at those pO2-levels which were optimal for CCl4-mediated lipid peroxidation. The present results demonstrate that CCl4 is a potent inducer of lipid peroxidation also in the intact hepatocyte, provided that the pO2 is maintained at distinct low levels. The coincidence of lipid peroxidation and loss of cell viability at the same pO2-range provides further evidence for the assumption that the haloalkane-mediated liver cell injury is due to a peroxidative process which primarily occurs at the hypoxic end of the physiological pO2-levels (1-70 mmHg) in liver.