HUMAN SECRETIN IS A GASTROINTESTINAL PEPTIDE HORMONE PRODUCED BY CELLS IN THE DUODENUM IN RESPONSE TO ACIDIFICATION. CHIRHOSTIM (HUMAN SECRETIN AS THE ACETATE) IS A PURIFIED SYNTHETIC PEPTIDE WITH AN AMINO ACID SEQUENCE IDENTICAL TO THE NATURALLY OCCURRING HORMONE. THE PRIMARY ACTION OF SECRETIN IS TO INCREASE THE VOLUME AND BICARBONATE CONTENT OF SECRETED PANCREATIC JUICES.
SECRETIN IS A HORMONE THAT IS NORMALLY RELEASED FROM THE DUODENUM UPON EXPOSURE OF THE PROXIMAL INTESTINAL LUMEN TO GASTRIC ACID, FATTY ACIDS AND AMINO ACIDS. SECRETIN IS RELEASED FROM ENTEROCHROMAFFIN CELLS IN THE INTESTINAL MUCOSA. SECRETIN RECEPTORS HAVE BEEN IDENTIFIED IN THE PANCREAS, STOMACH, LIVER, COLON AND OTHER TISSUES. WHEN SECRETIN BINDS TO SECRETIN RECEPTORS ON PANCREATIC DUCT CELLS IT OPENS CYSTIC FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR (CFTR) CHANNELS, LEADING TO SECRETION OF BICARBONATE-RICH-PANCREATIC FLUID. SECRETIN MAY ALSO WORK THROUGH VAGAL-VAGAL NEURAL PATHWAYS SINCE STIMULATION OF THE EFFERENT VAGUS NERVE STIMULATES BICARBONATE SECRETION AND ATROPINE BLOCKS SECRETIN-STIMULATED PANCREATIC SECRETION.