Parietal cells acetylcholine receptor

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... 

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. 

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... 

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. 

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... 

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-... 

Agents which block the acetylcholine receptor are known as anticholinergic drugs (see Chapter 11). These agents certainly block the cholinergic receptor in parietal cells and inhibit release of gastric acid. Unfortunately, they also inhibit acetylcholine receptors at other parts of the body and cause unwanted side-effects. 

Schematic representation of the resting (left side) and stimulated (right side) state of the parietal cell. Basolateral membrane contains three major receptor classes gastrin (G), acetylcholine (ACh), and histamine (H). Their actions are mediated by cAMP responses, Ca changes, or both. In addition, there are a number of ion transport pathways. In the stimulated state, the apical membrane acquires H", K -ATPase contained in the tubulovesicles (tv) as well as the property of K+ and CI conductance, both of which are essential in the secretion of HCl. A change in cytoskeletal arrangement is also associated with stimulation. CaM = calmodulin SC -secretory canaliculus mf = microfilaments. [Reproduced with permission from D. H. Malinowska and G. Sachs, Cellular mechanisms of acid secretion, Clin. Gastroenterol. 13, 322 (1984).]...

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