Gastrin

Gastrin is a peptide hormone, which is synthesized in cells of the mucosa of the gastric antrum and duodenum. It is secreted into the portal blood. The main effect of gastrin is the stimulation of secretion of acid by the parietal cells of the stomach. It also increases pepsinogen secretion and stimulates blood flow and gastric motility. The release of gastrin from G-cells in the gastric antrum is controlled by various mechanisms. Vagal stimulation to the antrum causes presynaptic release of acetylcholine, which causes the release of gastrin releasing peptide (GRP) from GRP-postsynaptic neurons, which directly stimulates the endocrine release of gastrin from G-cells. G-cells are also stimulated to release gastrin in response to protein digestion products on the luminal surface. These include amino acids and small peptides, which act directly on the gastrin-secreting cells. The release of somatostatin from D-cells, which are localized in the vicinity of G-cells has a negative influence...