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a hormone substance (tissue hormone) secreted by the mucosa of the upper portion of the small intestine that participates in the regulation of pancreatic secretion. Secretin was discovered in 1902 by the British physiologists W. Bayliss and E. Starling. (Starling introduced the concept of the hormone into science in 1905 as a result of his study of secretin.)
Chemically, secretin is a peptide consisting of 27 amino-acid residues, 14 of which are in the same sequence as in glucagon. Secretin is obtained in a pure form from the intestinal mucosa of swine. It is released mainly under the influence of the hydrochloric acid of gastric juice, which enters the duodenum with chyme, a gruel-like material. Secretion can be induced experimentally by introducing dilute acid into the small intestine.
Secretin is absorbed by the blood and travels to the pancreas, where it intensifies the secretion of water and electrolytes, especially bicarbonate. Secretin increases the volume of pancreatic juice secreted but does not affect the production of pancreatic enzymes. The latter function is performed by pancreozymin, a substance elaborated in the intestinal mucosa. The biological determination of secretin is based on its ability to make the pancreatic juice more alkaline when injected intravenously into animals. Secretin has been synthesized chemically.
REFERENCESClegg. C., and A. Clegg. Gormony, kletki, organizm, ch. 13. Moscow, 1971. (Translated from English.)
Gastrointestinal Hormones. Stuttgart, 1972.
A. A. BULATOV