Gastric acid secretion paracrine

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. 

A synopsis of the most important data concerning H3 receptors and gastric acid secretion is reported in Tables 1 and 2. Table 3 reports the effects of H3 ligands on hormonal or paracrine secretions which are directly or indirectly connected with acid secretion. 

The peripheral regulation of gastric acid secretion involves several mechanisms including neural, hormonal, paracrine and autocrine elements. The common goal of these regulatory mechanisms is to modulate gastric acid secretion by the parietal cell in response to different levels of stimuli such as acetylcholine, histamine and gastrin. 

The substantial production and metabolism of dopamine in the human GI tract appear to reflect functions of dopamine as an enteric neuromodulator or paracrine and/or autocrine substance. Dopamine and dopamine receptor agonists stimulate bicarbonate secretion and protect against ulcer formation, whereas dopamine antagonists augment secretion of gastric acid and promote ulcer development. Dopamine also appears to influence GI motility, sodium transport, and gastric and intestinal submucosal blood flow. In the pancreas, dopamine may modulate secretion of digestive enzymes and bicarbonate. 

Some of the receptors defined on the gastric endocrine/paracrine system. The ECL and G cells upregulate acid secretion, and the D cell inhibits acid secretion. The ECL cell expresses the CCKj or gastrin receptor and the somatostatin type 2 receptor and PAC1, the PACAP receptor. The G cells express a stimulatory muscarinic receptor subtype not known and a stimulatory GRP receptor and an inhibitory somatostatin type 2 receptor. The D cell has stimulatory CCK, and CCK, receptors and inhibitory muscarinic (either Mj or AA,) receptors. 

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