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M.Prasad Naidu MSc Medical Biochemistry, Ph.D.Research Scholar Hormones of GIT
gastrin • Produced by the pyloric mucosa • Secretion of gastrin is stimulated by the proteins present in food or HCl • gastrin is absorbed into the blood and is carried to the fundic cells, causing them to secrete HCl actively. • Gastrin stimulates the gastric glands to pour out more gastric juice. • Gastrin is hexa peptide (mol.wt 2100) • It dialyzes through a membrane & has a PI 5.5
Secretin • The 1st compound to be designated as hor • Formed by the upper intestinal mucosa • Liberated by HCl present in the acid chyme (semi fluid material present in stomach). • It is carried by the blood to pancreas which it stimulates the flow of P.juice rich in HCO3-. • Also stimulates the secretion of bile and intestinal juices. • Obtained in a crystalline form—PP or 27 AAs mol wt 3056.
cholecystokinin • Also secreted by up part of S. intestine. • Stimulates the contraction of gall bladder • CCK is a PP – 33AAs– 3883 • Enterogastrone:- present in Duo.mucosa • Secretion is stimulated by FAT ↓ gastric secretion & motility of stomach.
pancreozymin • PP hormone (33AAs) • Stimulates secretion of P.juice • The secretion of PZ is stimulated in the presence of peptone, casein, dextrin, maltose, lactose, saline water & dist.water • It is thermostable & not destroyed by acid but is destroyed by alkali • CCK and PZ are thought to be similar hence, represented as CCK-PZ.
Other GIT hormones • enterokinin:- isolated from intstinal mucosa and controls the intestinal secretion. • EK ↑ vol & enzyme conc.of succus entericus. • Proteinacious in nature & stimulates the secretion of both fluid and enzymes by the intestinal mucosa. • Hepatocrinin:- it is related to EK and is believed to stimulate the secretion of dilute, low-salt type of bile juice.
Other GIT hormones • Duicrinin:- controls the secretion of Brunner’s glands which are located in the submucosa of the upper duodenum. • Villikinin:- secreted by inte.mucosa • Stimulates the movements of the I.villi and hence accelerates intestinal absorption. • Parotin:- protein hormone • Stimulates calcification of teeth & decreases the conc.of Ca content of blood • Increases the P level of the serum.