Parietal cells gastrin receptor

Kopin AS, Lee YM, McBride EW, et al. Expression cloning and characterization of the canine parietal cell gastrin receptor. Proc Natl Acad Sci U S A 1992 89 3605-3609. 

The parietal cell contains receptors for gastrin (CCK-B), histamine (H2), and acetylcholine (muscarinic, M3) (Figure 62-1). When acetylcholine (from vagal postganglionic nerves) or gastrin (released from antral G cells into the blood) bind to the parietal cell receptors, they cause an increase in cytosolic calcium, which in turn stimulates... 

Parietal cells possess receptors for three stimulators of acid secretion neural (acetylcholine, muscarinic-type receptor), paracrine (gastrin) and endocrine control (histamine, H2 type receptor) (Figure 4.2). 

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... 

Interaction of the food with the gastric mucosal layer is the normal trigger for gastric cells to release gastrin, which is then carried by the bloodstream to the parietal cells. Calcium ions and cyclic AMP act as intracellular messengers in the transfer of the signal from the receptors to the proton pumps of parietal cells where the acid is generated. 

Ib. Inhibitors of add production. Acting on their respective receptors, the transmitter acetylcholine, the hormone gastrin, and histamine released intra-mucosally stimulate the parietal cells of the gastric mucosa to increase output of HCl. Histamine comes from entero-chromaffin-like (ECL) cells its release is stimulated by the vagus nerve (via Mi receptors) and hormonally by gastria The effects of acetylcholine and histamine can be abolished by orally applied antagonists that reach parietal cells via the blood. 

Histamine receptors on parietal cells belong to the H2 type (p. 114) and are blocked by H2-antihistaniines. Because histamine plays a pivotal role in the activation of parietal cells, H2-anti-histamines also diminish responsivity to other stimulants, e.g gastrin (in gas-2000 Thieme... 

Hormonal gastrin secreted by the G cells of the gastric antrum stimulates the parietal cells directly through gastrin receptors (increased Ca2+ as second messenger), and probably also indirectly by acting on enterochromaffin-iike (ECL) cells to release histamine. 

In close proximity to the parietal cells are gut endocrine cells called enterochromaffin-like (ECL) cells. ECL cells also have receptors for gastrin and acetylcholine, which stimulate histamine release. Histamine binds to the H2 receptor on the parietal cell, resulting in activation of adenylyl cyclase, which increases intracellular cyclic adenosine... 

Schematic diagram of one model of the physiologic control of hydrogen ion secretion by the gastric parietal cell. ECL cell, enterochromaffin-like cell G(CCK-B), gastrin-cholecystokinin-B receptor H, histamine H2, histamine H2 receptor Mi, M3, muscarinic receptors ST2, somatostatin2 receptor ATPase, K /H ATPase proton pump. Some investigators place histamine receptors—and possibly cholinoceptors—on nearby tissue cells rather than on the parietal cell itself. (Modified and redrawn from Sachs G, Prinz C Gastric enterochromaffin-like cells and the regulation of acid secretion. News Physiol Sci 1996 11 57, and other sources.)...

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. 

As the H+ is pumped into the lumen of the stomach, HC03 moves out of parietal cells into blood and Cl- enters the cell in exchange. Acid secretion is stimulated by histamine acting on H2 receptors, by acetylcholine acting on muscarinic (Ml) receptors and by gastrin acting on gastrin receptors of the parietal cells. 

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

The binding of histamine to its Hj-receptor on the parietal cell causes activation of the membrane-bound adenylate cyclase with a corresponding increase in intracellular cyclic AMP levels. The binding of acetylcholine or gastrin to their specific receptors increases intracellular calcium. Increased... 

Gastric acid is secreted by the parietal cells in gastric mucosa. The basolateral membranes of these cells contain receptors for the three main stimulants of acid secretion, namely gastrin (from antral G cells), histamine (from enterochromaffin-Uke cells) and acetylcholine (from vagal efferents). The action... 

The stomach secretes hydrochloric acid under the influences of vagus nerve stimulation, gastrin and histamine. Histamine is the most potent stimulus of gastric acid secretion in some animal species studied, such as the horse (Kitchen et al 1998a). Histamine is released by mast cells and enterochromaffin-like cells that are immediately adjacent to the parietal cells. Histamine interacts with two distinct subsets of histamine H2 receptors on the parietal cell membrane, initiating a series of reactions that result in the phosphorylation of protein kinases and increased intracellular calcium within the parietal cell. This, in turn, results in transformation and translocation of the... 

Therefore, there seems to be a complex interaction among the three receptors, acetylcholine receptors, H2 receptors, and gastrin receptors involved in the acid secretion by parietal cells. 

The mechanism of acid secretion is stiU widely debated there is, however, significant agreement that acetylcholine, histamine, and gastrin act through their respective neuro-crine, paracrine, and endocrine pathways to stimulate the parietal cells, and that specific parietal cell receptors to these transmitters exist. Also, there are potentiating interactions between the mentioned secretagogues that probably occur at the parietal ceil itself. Histamine has a role as a mediator or a potentiator of the actions of other secretagogues. Admin-... 

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