C O N T E N T SSee AlsoDescriptionIn humans, gastrin is a hormone that stimulates secretion of gastric acid by the stomach. It is released by G cells in the stomach and duodenum. GeneticsThe GAS gene is located on the long arm of the seventh chromosome (17q21). Synthesis and releaseGastrin is a linear peptide hormone produced by G cells that are located mainly in the antrum of the stomach and the D cells of the pancreatic islets. It is secreted into the bloodstream. Gastrin is found primarily in three forms: gastrin-34 ("big gastrin"), gastrin-17 ("little gastrin"), and gastrin-14 ("minigastrin"). The numbers refer to the amino acid count. Gastrin is released in response to certain stimuli. These include: stomach distension, vagal stimulation (mediated by the neurocrine bombesin, or GRP in the human), the presence of partially digested proteins especially amino acids and hypercalcemia. Gastrin release is inhibited by the presence of acid (primarily the secreted HCl) in the stomach (a case of negative feedback). Somatostatin also inhibits the release of gastrin, along with secretin, GIP, VIP, glucagon and calcitonin. FunctionThe presence of gastrin stimulates parietal cells of the stomach to secrete hydrochloric acid (HCl)/gastric acid. This is done either directly or indirectly:
It also causes chief cells to secrete pepsinogen, the zymogen (inactive) form of the digestive enzyme pepsin. Pepsinogen is converted to pepsin in a low pH environment, and the HCl provides a suitable environment for its activity. It can also increase antral muscle mobility and trophic effect on GI tract. Gastrin has also been shown to induce production of pancreatic enzymes by acinar cells. Factors influencing secretionGastric lumen:
Paracrine:
Nervous:
Circulation:
Role in diseaseIn the Zollinger-Ellison syndrome, gastrin is produced at excessive levels, often by a gastrinoma (gastrin-producing tumor, mostly benign) of the antrum or the pancreas. To investigate for hypergastrinemia (high blood levels of gastrin), a "pentagastrin test" can be performed. LinksAttribution
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