alpha-Momorcharin, beta-momorcharin and trichosanthin increased the secretion of glutamate-pyruvate transaminase, lactate dehydrogenase and isocitrate dehydrogenase by isolated rat hepatocytes into the culture medium. This hepatotoxic effect of the proteins appeared to be concentration-dependent. The plant proteins induced morphological changes in hepatocytes including increased formation of cytoplasmic blebs and a reduction of microvilli on plasma membrane.