Activities of Key Gluconeogenic Enzymes and Glycogen Synthase in Rat and Human Livers, Hepatomas, and Hepatoma Cell Cultures1

The activities of pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (GGPase), and glycogen synthetase (GS) were determined in the cancerous and in the apparently uninvolved (host) regions of livers from primary hepatoma patients as well as in normal adult human livers and human fetal livers. The activities of these enzymes were also assayed in a fairly fast-growing, 3 -methyl-4-dimethylaminoazobenzene-induced transplantable rat hepatoma and in hepatoma cell lines derived from both rat and human tumors. In the human hepatoma, as in the rat hepatoma, the activities of PC, PEPCK, and GSPase were considerably reduced, compared to those in the host liver. The activi ties of both the a (glucose 6-phosphate-independent) and b (glucose 6-phosphate-dependent) forms of GS were also lower in human and rat hepatomas than in the respective host livers. Activities of PC, PEPCK, and G6Pase in the human hepatomas were often comparable with those of fetal livers. In rat and human hepatoma cells, the activi ties of PC, PEPCK, and GGPase were similar to or lower than the activities in the respective hepatomas; the activ ities of GS a were also similar to those in the hepatoma, whereas the activities of GS b were somewhat higher.