harmone of the adenohypophysis of pancreas as well as by some cells of the gastro intestin

derived from a bigger prohormone molecule (mol wt 9000) Non pancreatic sources of glucagon at least in some animais. some cells of the gaslromtesli- nal tract particularly those of the duodenum produce a closely related substance called entero glue agon. Plasma concentration of glucagon In normal persons is about 50 to 110 pg/ml Functions Glucagon can be largely viewed as an anti insulin hormone its major action is to raise blood sugar level This is done by the _following mechanisms (i) glucagon tnh nces Irver glycogenolysis (glycogen of the liver is converted into glucose and released into the blood), (n) it enhances glaconeogenesis In addition, glucagon can increase adipose tissue lipofysis. but m the intact man, thrs is not of great importance It is viewed by some authors that insulin and gluts act as a pair to control (stabilize) blood sugar level and carbohydrate metabolism As staled before, glucagon by its paracrine effecl stimulates insulin secietion Regulation of glucagon secretion 1 Most important regulator is blood sugar concentration A low level of blood sugar stimulates glucagon secretion and blood sugar homeostssis i$ regatnvd (substrate regulation) theriby 2 Rise in plasma ammo acid level causes stimulation of glucagon secretion 3 Some gastrointestinal hormones cause stimulation of glucagon secretion 4 Insulin exerts a paracnne effect on o cells. By this local action, insulin inhibits glucagon release OTHER PANCREATIC HORMONES Somatostatin This hormone as slated earlier (chap S sec Vl)r is produced by the hypolbalarnus and there its major action is to inhibit the release of growth harmone of the adenohypophysis