Gastric acid secretion endocrine

Gastric acid secretion can be inhibited by several mechanisms including acid in the stomach (pH 3 inhibits gastrin release), acid in the duodenum, the presence of fat in the pancreas, and hypertonic fluids or hyperglycemia. Somatostatin, a hormone produced by antral mucosal endocrine cells (D cells), inhibits the release of gastrin by directly inhibiting the parietal cells. Somatostatin is also present in other GI tissue and the pancreas. C cells, endocrine cells in the proximal small intestine, secrete secretin in response to mucosal acidification, which also decreases gastric secretion. 

The involvement of more than one endocrine hormone and neurotransmitter in the control of gastric acid secretion has resulted in a number of therapeutic approaches directed toward achieving its inhibition. Of these strategies both muscarinic and histamine Hg-receptor antagonists have been used, with the latter being the method of choice for the control of acid-related disorders, particularly peptic ulcer disease, until the late 1980s. Along with the successful treatment of many patients... 

Pancreatic polypeptide (PP) Endocrine cells in periphery of islets in the head of the pancreas 1. Reduces CCK-mediated gastric acid secretion 2. Increases intestinal transit time (slows motility) Stimulated by intraluminal nutrients, hypoglycemia, and vagal nerve stimulation... 

Acetylcholine is released from the postganglionic fibers of the enteric nervous system and regulates gastric acid secretion both by directly acting on the parietal cell and indirectly stimulating several endocrine cells, which in turn modulate the activity of the parietal cell [6]. Five subtypes of the... 

Gastrin is a hormone produced by gastric endocrine tissue — specifically, the G cells in the pyloric gland area. It is released into the blood and carried back to the stomach. The major function of gastrin is to enhance acid secretion by directly stimulating parietal cells (HC1) and chief cells (pepsinogen). Gastrin also stimulates the local release of histamine from enterochromaf-fin-like cells in the wall of the stomach. Histamine stimulates parietal cells to release HC1. 

The oxyntic gland is the secretory unit of the gastric mucosa. The acid-secreting parietal cells are located in the wall of its midsection. In addition to parietal cells, these glands consist of mucous-secreting superficial and neck cells, pepsinogen-secreting chief cells, endocrine, and somatostatin cells [1]. 

The pancreas possesses both endocrine and exocrine fnnctions. The islets of Langerhans, which contain the cells of the endocrine pancreas, secrete insnlin, glncagon, somatostatin, and other polypeptide hormones. The exocrine pancreas is composed of acini that secrete about 1 to 2 L/day of isotonic fluid that contains water, electrolytes, and pancreatic enzymes necessary for digestion. Bicarbonate is secreted primarily by the centroacinar (ductular) cells, and is the principal ion of physiologic importance. Pancreatic juice is delivered to the duodenum via the pancreatic ducts (Fig. 39-1) where the alkaline secretion (pH about 8.3) neutralizes gastric acid and provides an appropriate pH for maintaining the activity of pancreatic enzymes."... 

Clinically important above all are examinations in patients with altered gastric secretion. A fair correlation is found between the content of pepsinogen in the gastric juice and in the serum. This is easily comprehensible as an expression of the bipolar (exo- and endocrine) function of the pepsin cells of the gastric mucosa. There exists, however, a clinically useful relationship between pepsinogen and gastric acidity, illustrated by the survey in Table X. 

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. 

Secretin Endocrine cells in mucosa of duodenum Acid in duodenum Inhibits gastric emptying and gastric secretion stimulates secretion of bicarbonate from pancreas stimulates secretion of bicarbonate-rich bile from liver... 

The presence of chyme in the duodenum stimulates neuronal and endocrine responses that stimulate and later inhibit secretion of acid into the stomach. The stimulatory influences dominate when the pH of gastric chyme is above 3. However, when the buffer capacity is exhausted and the pH falls below 2, inhibitory influences dominate. 

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