All of the following GIT hormones belong to secretin family except
Cholecystokinin (CCK) is secreted by cells in the mucosa of the upper small intestine. It has a plethora of actions in the gastrointestinal system, but the most impoant appears to be the stimulation of pancreatic enzyme secretion, the contraction of the gallbladder (the action for which it was named), and relaxation of the sphincter of Oddi, which allows both bile and pancreatic juice to flow into the intestinal lumen. Secretin is secreted by S cells that are located deep in the glands of the mucosa of the upper poion of the small intestine. The structure of secretin is different from that of CCK and gastrin, but very similar to that of glucagon, GLI, VIP, and GIP. Only one form of secretin has been isolated, and the fragments of the molecule that have been tested to date are inactive. Its half-life is about 5 minutes, but little is known about its metabolism.VIP contains 28 amino acid residues. It is found in nerves in the gastrointestinal tract and thus is not itself a hormone, despite its similarities to secretin.VIP is also found in blood, in which it has a half-life of about 2 minutes. In the intestine, it markedly stimulates intestinal secretion of electrolytes and hence of water. Its other actions include relaxation of intestinal smooth muscle, including sphincters; dilation of peripheral blood vessels; and inhibition of gastric acid secretion. It is also found in the brain and many autonomic nerves where it often occurs in the same neurons as acetylcholine. It potentiates the action of acetylcholine in salivary glands.REF: GANONG&;S REVIEW OF MEDICAL PHYSIOLOGY, KIM BARRETT, HEDDWEN BROOKS, SCOTT BOITANO, SUSAN BARMANTWENTY THIRD EDITIONPAGE NO:446,447
Secretin
Glucagon
CCK
VIP
G.I.T