title: Plasmalemmal V-H(+)-ATPases regulate intracellular pH in human lung microvascular endothelial cells.
abstract: The lung endothelium layer is exposed to continuous CO(2) transit which exposes the endothelium to a substantial acid load that could be detrimental to cell function. The Na(+)/H(+) exchanger and HCO(3)(-)-dependent H(+)-transporting mechanisms regulate intracellular pH (pH(cyt)) in most cells. Cells that cope with high acid loads might require additional primary energy-dependent mechanisms. V-H(+)-ATPases localized at the plasma membranes (pmV-ATPases) have emerged as a novel pH regulatory system. We hypothesized that human lung microvascular endothelial (HLMVE) cells use pmV-ATPases, in addition to Na(+)/H(+) exchanger and HCO(3)(-)-based H(+)-transporting mechanisms, to maintain pH(cyt) homeostasis. Immunocytochemical studies revealed V-H(+)-ATPase at the plasma membrane, in addition to the predicted distribution in vacuolar compartments. Acid-loaded HLMVE cells exhibited proton fluxes in the absence of Na(+) and HCO(3)(-) that were similar to those observed in the presence of either Na(+), or Na(+) and HCO(3)(-). The Na(+)- and HCO(3)(-)-independent pH(cyt) recovery was inhibited by bafilomycin A(1), a V-H(+)-ATPase inhibitor. These studies show a Na(+)- and HCO(3)(-)-independent pH(cyt) regulatory mechanism in HLMVE cells that is mediated by pmV-ATPases.
authors.affiliation: Department of Physiology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
authors.forename: José D
authors.initials: JD
authors.lastname: Rojas
authors.forename: Souad R
authors.initials: SR
authors.lastname: Sennoune
authors.forename: Debasish
authors.initials: D
authors.lastname: Maiti
authors.forename: Gloria M
authors.initials: GM
authors.lastname: Martínez
authors.forename: Karina
authors.initials: K
authors.lastname: Bakunts
authors.forename: Donald E
authors.initials: DE
authors.lastname: Wesson
authors.forename: Raul
authors.initials: R
authors.lastname: Martínez-Zaguilán
mesh_terms: D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000737:chemistry / Q000378:metabolism*; D008168:Lung / Q000098:blood supply / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D008833:Microcirculation / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D025262:Vacuolar Proton-Translocating ATPases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D025262:Vacuolar Proton-Translocating ATPases