title: Vacuolar-type H+-ATPase-mediated proton transport in the rat parietal cell.
abstract: The vacuolar-type H-ATPase (V-ATPase) plays an important role in the active acidification of intracellular organelles. In certain specialized cells, such as the renal intercalated cell, apical V-ATPase can also function as a proton secretion pathway. In the parietal cells of the stomach, it has been thought that acid secretion is controlled solely via the H,K-ATPase. However, recent observations suggest that functional V-ATPase is necessary for acid secretion to take place. This study aimed to investigate and characterize the role of V-ATPase in parietal cell proton transport. Individual rat gastric glands were incubated with the pH-sensitive dye (BCECF) to monitor changes in intracellular pH in real time. Parietal cell V-ATPase activity was measured by quantifying the rate of intracellular alkalinization (ΔpH/minute) following an acid load, while excluding the contribution of non-V-ATPase proton transport mechanisms through pharmacological inhibition or ion substitution. Expression of V-ATPase was confirmed by immunohistochemistry. We observed concanamycin A-sensitive V-ATPase activity in rat parietal cells following intracellular acidification and H,K-ATPase inhibition. Furthermore, V-ATPase-mediated proton transport could be abolished by inhibiting trafficking mechanisms with paclitaxel and by stimulating H,K-ATPase with acid secretagogues. Our results propose that parietal cells contain a functional V-ATPase that can be mobilized using a microtubule network. V-ATPase may function as an auxiliary acid secretion or proton-buffering pathway in parietal cells, which is inactive during H,K-ATPase activity. Our findings may have important implications for patients experiencing acid breakthrough under proton pump inhibitor therapy.
authors.affiliation: Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT, USA.
authors.forename: Sascha
authors.initials: S
authors.lastname: Kopic
authors.forename: Maximilian E H
authors.initials: ME
authors.lastname: Wagner
authors.forename: Christoph
authors.initials: C
authors.lastname: Griessenauer
authors.forename: Thenral
authors.initials: T
authors.lastname: Socrates
authors.forename: Markus
authors.initials: M
authors.lastname: Ritter
authors.forename: John P
authors.initials: JP
authors.lastname: Geibel
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D017136:Ion Transport; D018942:Macrolides / Q000494:pharmacology; D010295:Parietal Cells, Gastric / Q000187:drug effects / Q000378:metabolism*; D010418:Pentagastrin / Q000494:pharmacology; D018892:Proton-Motive Force; D051381:Rats; D017207:Rats, Sprague-Dawley; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D018942:Macrolides; C036978:concanamycin A; D006632:Histamine; D002217:Carbachol; D025262:Vacuolar Proton-Translocating ATPases; D010418:Pentagastrin; D000109:Acetylcholine