title: Bufo marinus bladder H-K-ATPase carries out electroneutral ion transport.
abstract: Bufo marinus bladder H-K-ATPase belongs to the Na-K-ATPase and H-K-ATPase subfamily of oligomeric P-type ATPases and is closely related to rat and human nongastric H-K-ATPases. It has been demonstrated that this ATPase transports K(+) into the cell in exchange for protons and sodium ions, but the stoichiometry of this cation exchange is not yet known. We studied the electrogenic properties of B. marinus bladder H-K-ATPase expressed in Xenopus laevis oocytes. In a HEPES-buffered solution, K(+) activation of the H-K-ATPase induced a slow-onset inward current that reached an amplitude of approximately 20 nA after 1-2 min. When measurements were performed in a solution containing 25 mM HCO at a PCO(2) of 40 Torr, the negative current activated by K(+) was reduced. In noninjected oocytes, intracellular alkalization activated an inward current similar to that due to B. marinus H-K-ATPase. We conclude that the transport activity of the nongastric B. marinus H-K-ATPase is not intrinsically electrogenic but that the inward current observed in oocytes expressing this ion pump is secondary to intracellular alkalization induced by proton transport.
authors.affiliation: Institut de Pharmacologie et de Toxicologie, CH-1005 Lausanne, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Burnay
authors.forename: G
authors.initials: G
authors.lastname: Crambert
authors.forename: S
authors.initials: S
authors.lastname: Kharoubi-Hess
authors.forename: K
authors.initials: K
authors.lastname: Geering
authors.forename: J D
authors.initials: JD
authors.lastname: Horisberger
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D001692:Biological Transport; D002024:Bufo marinus; D002245:Carbon Dioxide / Q000494:pharmacology; D004553:Electric Conductivity; D005260:Female; D015870:Gene Expression; D017506:H(+)-K(+)-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials; D009865:Oocytes / Q000378:metabolism; D012414:Rubidium Radioisotopes / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014162:Transfection; D001743:Urinary Bladder / Q000201:enzymology*; D014982:Xenopus laevis
chemical_list: D001639:Bicarbonates; D012414:Rubidium Radioisotopes; D002245:Carbon Dioxide; D017506:H(+)-K(+)-Exchanging ATPase; D000254:Sodium-Potassium-Exchanging ATPase; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid