AIM:To study the effect of hepatocyte apoptosis and necrosis induced by TNF-alpha on the pathogenesis of acute severe hepatitis (ASH).METHODS:The model of ASH was prepared in D-galactosamine (GalN) sensitized BALB/c mice by injection of either endotoxin (ET) or tumor necrosis factor-alpha(TNF-alpha. Morphological changes of apoptotic hepatocytes were studied by both light and electron microscope and in site end labeling method (ISEL). Molecular biological changes of DNA ladder were observed by electrophoresis of extract from liver tissues. Biochemical changes were measured by alanine aminotransferase (ALT), aspartic aminotransferase (AST) and TNF-alpha. The relation between apoptosis and necrosis was evaluated simultaneously.RESULTS:The sequence of hepatocyte apoptosis, necrosis, and final death from ASH was observed both in GalN/ET and GalN/TNF-alpha group. Apoptosis was prominent at 3.5h and 6h after injection of inducer, while necrosis became dominant at 9h after challenge. The appearance of apoptosis was earlier in GalN/TNF-alpha group than that in GalN/ET group. Pretreatment of mice with antiTNF IgG1 may completely prevent the liver injury induced by GalN/ET.CONCLUSION:TNF-alpha can cause liver amage by inducing hepatic apoptosis and necrosis in mice with endotoxemia.