Gastric acid secretion regulation

Histamine is a biogenic amine that is widely distributed in the body and functions as a major mediator of inflammation and allergic reactions, as a physiological regulator of gastric acid secretion in the stomach, as a neurotransmitter in the central nervous system (CNS) and may also have a role in tissue growth and repair. 

Gastrointestinal Erosive gastritis, peptic ulceration PGE2-mediated suppression of gastric acid secretion, which helps maintain mucosal barrier and regulate microcirculation COX-1... 

TEicosanoids are paracrine hormones, substances that act only on cells near the point of hormone synthesis instead of being transported in the blood to act on cells in other tissues or organs. These fatty acid derivatives have a variety of dramatic effects on vertebrate tissues. They are known to be involved in reproductive function in the inflammation, fever, and pain associated with injury or disease in the formation of blood clots and the regulation of blood pressure in gastric acid secretion and in a variety of other processes important in human health or disease. 

Soldani, G., Intorre, L., Bertini, S., Luchetti, E., Coruzzi, G., Bertaccini, G., 1994. Regulation of gastric acid secretion by histamine H3 receptors in the dogs an investigation into the site of action. Naunyn-Schmiedeberg s Arch. Pharmacol. 350, 218-223. 

Vuyyuru, L., Schubert, M L, 1993. Participation on histamine H3-receptors of the fundus in the regulation of gastric acid secretion. Gastroenterology 104 (Suppl), A220. 

H2 receptors are involved primarily in the regulation of gastric acid secretion. Drugs that selectively block the H2 receptor (referred to simply as H2 antagonists) may help control gastric secretion in conditions such as peptic ulcer these drugs are discussed in Chapter 27. 

Apart from its role as a major mediator of inflammation and allergic reactions and as physiological regulator of gastric acid secretion, histamine is also a neurotransmitter in the CNS. Central histaminergic cell bodies are located in the posterior hypothalamus and project diffusely to almost all brain regions and to the spinal cord. There are four types of histamine receptors, all G-protein-coupled, Hi, H2, H3 and H4. Hi receptors couple to Gq/11 proteins. H2 receptors couple to Gs. H3 and H4 receptors couple to Gi/o. 

The involvement of the proton pump (H+, K+-ATPase) in the regulation of gastric acid secretion by the parietal (oxyntic) cell is well established. 

Gastric acid secretion may be regulated by several brain peptides, some of which may enhance secretion, while others may act centrally to inhibit secretion. 

Receptor-Mediated Processes that Regulate Gastric Acid Secretion, 97... 

RECEPTOR-MEDIATED PROCESSES THAT REGULATE GASTRIC ACID SECRETION... 

Gastrin 17 Gastrin-17 G cellsin stomach, duodenum Appetite regulation Gastric acid secretion viahistaminerelease from APUD cells in gastric mucosa (enterochromaffin-like (ECL) cells) (Hj antagonist-sensitive)... 

PGE2 and PGF2CI stimulate synthesis of protective mucus in stomach and in small intestine. When ASA is administrated, prostaglandins and prostacyclins synthesis is blocked and acid secretion is increased, reducing mucosae protection. COX has two different isoforms COX-1, expressed in most tissues and implicated in the regulation of normal homeostatic functions such as gastric acid secretion and COX-2, induced often by inflammatory processes. As a result, COX-2 is implicated in the production of pro-inflammatory eicosanoids (see Figure 25). In feet, one of the therapeutic actions of ASA et similia NSAIDs has been the inhibition of COX activity to reduce pro-inflammatory eicosanoids [73]. 

The regulation of gastric acid secretion and the clinical utility of antagonists are discussed in Chapter 36. 

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