Secretin human

Synthetic human secretin mediates the same biological effects as the naturally-occurring gastrointestinal peptide hormone. Secretin is normally released from enterochromaffin cells and S cells in the intestinal mucosa of duodenum upon exposure of proximal intestinal lumen to the acidic gastric content, or fatty acids and amino acids. Secretin mediates an inhibitory effect on acid secretion by parietal cells of the stomach, and causes alkalinazation of the duodenal content by stimulating the release of pancreatic juice, which has high amounts of water and bicarbonate ions. Bicarbonate ions are released into the duodenum from the centroacinar cells, and epithelia lining the pancreatic and biliary ducts. Human secretin is a ligand at G-protein coupled secretin receptors which are expressed in the basolateral domain of several tissue cell types, including pancreas, stomach, liver, colon and other tissues. Upon interaction, levels of cAMP increase and initiates the cAMP-mediated signalling cascade that results in phosphorylation of protein kinase A (PKA) and activation of cystic fibrosis transmembrane conductance regulator (CFTR). Activation of CFTR activates Cl-/HCO3- anion exchanger 2 and leads to secretion of bicarbonate-rich-pancreatic fluid. Via the same cAMP signalling pathway, secretin promotes the secretion of water and electrolytes in cholangiocytes. Secretin may work through vagal-vagal neural pathways since stimulation of the efferent vagus nerve stimulates bicarbonate secretion and atropine blocks secretin-stimulated pancreatic secretion. Additionally, secretin acts as a diuretic to increase urinary volume and bicarbonate excretion.