Gastric acid secretion gastrin

The histamine H2-receptor (359 amino acids) is best known for its effect on gastric acid secretion. Histamine H2-receptor activation, in conjunction with gastrin and acetylcholine from the vagus, potently stimulate acid secretion from parietal cells. High concentrations of histamine are also present in cardiac tissues and can stimulate positive chronotropic and inotropic effects via H2-receptor stimulation and activation of adenylyl... 

The gastric acid secretion can be stimulated by the transmitters acetylcholine, histamine and the hormone gastrin. Histamine, acting via H2-receptors,... 

Gastric acid secretion is inhibited in the presence of acid itself. A negative feedback occurs when the pH approaches 2.5 such that further secretion of gastrin is inhibited until the pH rises. Ingested carbohydrates and fat also inhibit acid secretion after they reach the intestines several hormonal mediators for this effect have been proposed. The secretion of pepsinogen appears to parallel the secretion of H+, while the patterns of secretion of mucus and bicarbonate have not been well characterized. 

A. Gastrin, histamine, and acetylchohne stimulate gastric acid secretion. Pepsin is a digestive protein secreted by the stomach in response to a meal. Norepinephrine is a neurotransmitter that does not affect gastric acid secretion. 

Stimulation of gastric acid secretion is the most important response it is blocked only by Hj antagonists. As mentioned before, the hormone gastrin may be involved in histamine release, because Hj antagonists block gastrin-induced acid secretion. 

PGE s PGI also inhibit gastric acid secretion stimulated by gastrin or histamine. 

Actions The histamine H2-receptor antagonists—cimetidine, ranitidine, famotidine, and nizatidine—act on H2-receptors in the stomach, blood vessels, and other sites. They are competitive antagonists of histamine and are fully reversible. These agents completely inhibit gastric acid secretion induced by histamine, or gastrin. However, they only partially inhibit gastric acid secretion induced by acetylcholine or bethanechol. 

Effects of acetylcholine, histamine, prostaglandin I2, and E2, and gastrin on gastric acid secretion by the parietal cells of stomach Gs and Gj are membrane proteins that mediate the stimulatory or inhibitory effect of receptor coupling to adenylyl cyclase. 

Barrett AM (1966) Specific stimulation of gastric acid secretion by a pentapeptide derivative of gastrin. J Pharm Pharmac 18 633-639... 

Lawrence AJ, Smith GM (1974) Measurement of gastric acid secretion by conductivity. Eur J Pharmacol 25 383-389 Smith GM, Lawrence AJ, Colin-Jones DG, Schild HO (1970) The assay of gastrin in the perfused rat stomach. Br J Pharmacol 38 206-213... 

There are a variety of peptide hormones acting in the gut the gastrins stimulate gastric acid secretion secretin and somatostatin inhibit the production of gastrins. Cholecystokinin and somatostatin can inhibit gastric acid secretion directly, and the former one causes the gall-bladder to contract and thus force bile into the duodenum. 

Gastrin stimulates gastric acid secretion but also has growth-promoting effects on various cell types. Gastrin shares GPCRs with CCK, namely the CCK- A and -B receptors. 

Secretin inhibits postprandial gastrin release (thus decreasing gastric acid secretion) and increases pancreatic exocrine secretion (e.g. of bicarbonate). The secretin receptor (like the GLP-1 receptor and vasoactive intestinal peptide (VIP) receptor) acts via Gas and cAMP elevation. A plant agonist for the secretin receptor has been isolated from the Thai anti-ulcer plant Croton sublyratus (plau-loi) (Table 5.8). 

Gastrin and cholecystokinin receptor ligands consisting of lH-imidazole-4-yl-benzooxazole derivatives, (II), prepared by Kalindjian (3) were effective in controlling excess gastric acid secretion. 

Additional mediators of gastric acid secretion include calcium, gastrin-releasing hormone and enkephalin, while opiate receptors have also been identified on parietal cells. 

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