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Parietal cells structure

Scott D, Besancon M, Sachs G, et al. The effect of antisecretory drugs on parietal cell structure and H/K ATPase levels in rabbit gastric mucosa in vivo. Dig Dis Sci 1994 39 2118. [Pg.166]

Proton pump inhibitors undergo rapid first-pass and systemic hepatic metabolism and have negligible renal clearance. Dose reduction is not needed for patients with renal insufficiency or mild to moderate liver disease but should be considered in patients with severe liver impairment. Although other proton pumps exist in the body, the H+,K+ ATPase appears to exist only in the parietal cell and is distinct structurally and functionally from other H+ -transporting enzymes. [Pg.1314]

The tubulovesicular and canalicular structures of the parietal cell are the only compartments in the body with an extremely low pH (1-2). [Pg.96]

There are currently four racemic PPIs available on the market omeprazole, lansoprazole, pantoprazole, and rabeprazole. (More recently, enantiomerically pure versions have also been studied and developed, e.g., S-omeprazole, marketed by AstraZeneca as esomeprazole see Chapter II-2.) Proton pump inhibitors share the same core structure, the substituted pyridylmethyl-sulfmyl-benzimidazole, but differ in terms of substituents on this core structure. The absolute requirements of the core structure for the activity of PPIs was not understood until it became clear that the active PPIs are derived from inactive prodrugs the prodrugs are transformed, in the acid-secreting parietal cells, by a unique cascade of chemical structural transformations leading to the active principle, a cyclic sulfenamide species. Inhibition of acid secretion in turn is then achieved by formation of covalent disulfide bonds with key cysteines of the (H+/K+)-ATPase. [Pg.133]

The apical membrane of the parietal cell forms, under nonsecretory conditions, tubulovesicular structures and, under secretory conditions, secretory cannaliculi. Its morphology depends on the secretory state of the parietal cell [14]. The lumen of the cannaliculi belongs to the extracellular compartment under secretory conditions Figure 4.1) and contains hydrochloric acid with a pH of about 1. H /K -ATPase exchanges protons for potassium ions across the apical surface. Thereby, the enzyme pumps out the protons against a proton gradient of 1 1,000,000. [Pg.236]

The effect of gastric HVK -ATPase inhibitors on enzyme activity (ATP cleavage) can be studied in vitro with partly purified HVK -ATPase preparations [27]. This assay has been used more effectively to study the mechanism of action of H /K -ATPase inhibitors in detail than to study the structure-activity relationship of such inhibitors [28]. Since HVK -ATPase inhibitors of the omeprazole-type need acid activation and the enzyme assay should be performed at neutral pH values, a pre-incubation period at the lowest possible pH of about 6 was used to initiate the acidic conversion of the test compound into its active principle. This reflects more the chemical instability of the test compound at neutral pH values than its effect during conditions of much higher acidity within the secretory cannaliculus of the parietal cell during acid secretion. Many chemically labile inhibitors are therefore very active in this test system. However, they do not cause an inhibition in more complex test systems and, therefore, are without any practical usefulness [28]. [Pg.239]

The structure-activity relationship of HVK -ATPase inhibitors of the omeprazole type is based on the balance between chemical stability at neutral pH values and acid-induced conversion into the active sulphenamide. Derivatives, which are too unstable at neutral pH, are very active in the test assay of partly purified HVK" -ATPase. This assay has been performed at pH 7.4 after preincubation at pH 6 of the enzyme protein with the derivative to be tested. The high activity was therefore the result of the conversion of the derivative in solutions of neutral pH values and this does not reflect the situation of high acidity within the secretory compartment of the parietal cell [28]. The derivatives which are very unstable at neutral pH do not inhibit gastric acid secretion in vivo because their transformation had already occurred prior to the active principle reaching the target enzyme. Chemically very stable derivatives do not show any inhibitory effect either in vitro or in vivo. [Pg.244]

Scarff K L, Judd L M, Toh B H et al 1999 Gastric H(+), K(+)-adenosine triphosphatase beta subunit is required for normal function, development and membrane structure of mouse parietal cells. Gastroenterology 117 605-618... [Pg.119]

Synonyms Zantac Histamine blocker Antacid N,N-Dimethyl-5-(2-(l-methylamino-2-nitrovinyl-amino)-ethylthiomethyl)furfurylamine Chemical/Pharmaceutical/Other Class A competitive inhibitor of the H2 receptor located on the gastric parietal cells Chemical Structure ... [Pg.2204]

Comparison of the structures of histamine with cimetidine and ranitidine. The latter two are H2-receptor antagonists and act on the gastric parietal cells to inhibit gastric acid production. Ranitidine, which has a furan rather than an imidazole structure, is a more potent competitive inhibitor than cimetidine. [Pg.206]

Whereas the PPIs have a unique targeting and covalent inhibitory action on the proton pump based on their chemistry and the biology of the parietal cell, another class of compounds-acid pump antagonists-have a structural specificity... [Pg.136]


See other pages where Parietal cells structure is mentioned: [Pg.28]    [Pg.173]    [Pg.613]    [Pg.214]    [Pg.59]    [Pg.417]    [Pg.244]    [Pg.83]    [Pg.83]    [Pg.104]    [Pg.551]    [Pg.1223]    [Pg.143]    [Pg.95]    [Pg.97]    [Pg.105]    [Pg.75]    [Pg.133]    [Pg.921]    [Pg.651]    [Pg.275]    [Pg.380]    [Pg.949]    [Pg.99]    [Pg.129]    [Pg.1547]    [Pg.234]    [Pg.3]    [Pg.4]    [Pg.107]    [Pg.125]    [Pg.367]    [Pg.73]    [Pg.107]    [Pg.112]    [Pg.117]    [Pg.118]   
See also in sourсe #XX -- [ Pg.4 , Pg.71 ]




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Parietal cells

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