title: Demonstration of a functional apical sodium hydrogen exchanger in isolated rat gastric glands.
abstract: Previous studies have shown that gastric glands express at least sodium-hydrogen exchanger (NHE) isoforms 1-4. Our aim was to study NHE-3 localization in rat parietal cells and to investigate the functional activity of an apical membrane NHE-3 isoform in parietal cells of rats. Western blot analysis and immunohistochemistry showed expression of NHE-3 in rat stomach colocalizing the protein in parietal cells together with the beta-subunit of the H(+)-K(+)-ATPase. Functional studies in luminally perfused gastric glands demonstrated the presence of an apical NHE isoform sensitive to low concentrations of 5-ethylisopropyl amiloride (EIPA). Intracellular pH measurements in parietal cells conducted in omeprazole-pretreated superfused gastric glands showed an Na+-dependent proton extrusion pathway that was inhibited both by low concentrations of EIPA and by the NHE-3 specific inhibitor S3226. This pathway for proton extrusion had a higher activity in resting glands and was inhibited on stimulation of histamine-induced H(+)-K(+)-ATPase proton extrusion. We conclude that the NHE-3 isoform located on the apical membrane of parietal cells offers an additional pathway for proton secretion under resting conditions. Furthermore, the gastric NHE-3 appears to work under resting conditions and inactivates during periods of H(+)-K(+)-ATPase activity.
authors.affiliation: Department of Surgery, Yale University School of Medicine, New Haven, Connecticut 06511, USA.
authors.forename: Philipp
authors.initials: P
authors.lastname: Kirchhoff
authors.forename: Carsten A
authors.initials: CA
authors.lastname: Wagner
authors.forename: Florian
authors.initials: F
authors.lastname: Gaetzschmann
authors.forename: Klaus
authors.initials: K
authors.lastname: Radebold
authors.forename: John P
authors.initials: JP
authors.lastname: Geibel
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005753:Gastric Mucosa / Q000378:metabolism*; D006146:Guanidines / Q000494:pharmacology; D017506:H(+)-K(+)-Exchanging ATPase / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D007527:Isoenzymes; D008689:Methacrylates / Q000494:pharmacology; D009853:Omeprazole / Q000494:pharmacology; D010295:Parietal Cells, Gastric / Q000378:metabolism; D010477:Perfusion; D051381:Rats / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: C118956:3-(2-(3-guanidino-2-methyl-3-oxo-propenyl)-5-methylphenyl)-N-isopropylidene-2-methyl-acrylamide dihydrochloride; D004791:Enzyme Inhibitors; D006146:Guanidines; D007527:Isoenzymes; D008689:Methacrylates; C000613387:Slc9a3 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D006632:Histamine; D017506:H(+)-K(+)-Exchanging ATPase; D009853:Omeprazole; C039614:ethylisopropylamiloride