Hyperinsulinemia and hyperglucagonemia in fasted rats during liver regeneration

The two pancreatic hormones, insulin and glucagon, have been implicated as hepatotrophic factors for the regenerating liver after partial hepatectomy. Similar to previous studies, hyperglucagonemia and hypoinsulinemia were noted following major liver resection of initially well-fed rats. In contrast to well-fed animals, rats fasted for 24 h prior to surgery to deplete hepatic glycogen and establish low basal insulin levels developed both portal venous hyperglucagonemia and hyperinsulinemia after 67% hepatectomy. Elevation of basal portal venous levels of the two hormones suggested enhanced pancreatic secretion of insulin and glucagon in response to acute liver injury in fasted animals. Because polypeptide hormones must bind to specific hepatic cell membrane receptors to exert their hepatotrophic influences, basal portal-systemic venous differences of insulin and glucagon and glucose-elicited portal-hepatic venous insulin differences were evaluated. The evidence implies that hepatic extraction and, therefore, cell membrane receptor binding of both insulin and glucagon by regenerating livers were enhanced even though portal venous levels of the two hormones were elevated.