Effects of Gastrointestinal and Related Hormones on Glycogenolysis and Gluconeogenesis in Cultured Liver Cells1

Abstract

When isolated rat liver cells were incubated for 15 min in the presence of vasoactive intestinal peptide, secretin, gastrin, caerulein or glucagon at concentrations ranging from 0.2 microgram to 2 microgram per ml, glycogenolysis was stimulated. Among the gastrointestinal hormones or peptides tested, vasoactive intestinal peptide had the highest stimulatory activity. However, somatostatin was inhibitory for liver glycogenolysis. Combination experiments showed that somatostatin also inhibited the stimulatory effects of vasoactive intestinal peptide and secretin, but not that of glucagon, while glucagon and vasoactive intestinal peptide, or glucagon and secretin showed additive effects on glycogenolysis, but secretin and vasoactive intestinal peptide did not. The results suffest that the receptor site of glucagon is different from those of secretin and vasoactive intestinal peptide. Slight but significant stimulation of gluconeogenesis was also observed by vasoactive intestinal peptide and secretin. The evidence presented in this paper indicates that the so-called enterohepatic axis, in which a part of serum glucose levels is regulated directly by gastrointestinal hormones, exists and that the axis is inhibited by somatostatin.