Secretin is a peptide hormone, composed of 27 amino acids - of which 14 are homologous to the sequence of glucagon. It is produced in the S cells of the duodenum in the crypts of Lieberkühn. Its primary effect is to regulate the pH of the duodenal contents via the control of gastric acid secretion and buffering with bicarbonate. Secretin stimulates the secretion of bicarbonate (base) from the liver, pancreas, and duodenal Brunner's glands in order to buffer the incoming protons of the acidic chyme. It also enhances the effects of cholecystokinin. Secretin is known to promote the normal growth and maintenance of the pancreas. It counteracts blood glucose concentration spikes by triggering increased insulin release, following oral glucose intake. It also reduces acid secretion from the stomach by inhibiting gastrin release from G cells. This helps neutralize the pH of the digestive products entering the duodenum from the stomach, as digestive enzymes from the pancreas (e.g. pancreatic amylase and pancreatic lipase) function optimally at neutral pH.
Swiss-Prot Accession Number: P09683