Gastric secretions decreased by:
I. The three agonists of the parietal cell—gastrin, histamine, and acetylcholine—each bind to distinct receptors on the basolateral membrane. Gastrin and acetylcholine promote secretion by elevating cytosolic free calcium concentrations,whereas histamine increases intracellular cAMP.
II. A variety of substances are capable of reducing gastric acid secretion when infused intravenously, including prostaglandin E2 and several peptides hormones, including secretin, gastric inhibitory peptide, glucagon and somatostatin. PGE2, secretin and somatostatin may be physiologic regulators.
III. Somatostatin inhibits secretion of gastrin and histamine, and appears to have a direct inhibitory effect on the parietal cell.