title: Potassium secretion is inhibited by metabolic acidosis in rabbit cortical collecting ducts in vitro.
abstract: The role of metabolic acidosis in the regulation of transepithelial potassium transport was examined in rabbit cortical collecting ducts (CCD) using in vitro isolated tubular microperfusion and conventional microelectrode techniques. Basolateral metabolic acidosis, created by reduction of bicarbonate concentration from 25 to 5 meq/l, pH 7.40 to 6.80, depolarized the transepithelial voltage significantly (-6.5 +/- 1.0 to -2.7 +/- 1.3 mV). Basolateral acidosis also suppressed net potassium secretion (-14.3 +/- 2.1 to -9.0 +/- 1.7 pmol.min-1.mm-1). Electrophysiological study in CCD cells demonstrated that basolateral metabolic acidosis depolarized transepithelial voltage and apical and basolateral membrane voltage with an increase of transepithelial and fractional apical resistance. Basolateral acidosis did not affect the 22Na efflux nor 86Rb efflux. The inhibitory action of basolateral acidosis on net potassium secretion remained in the presence of luminal barium and in the absence of bicarbonate. Ouabain could not abolish the effect of basolateral acidosis on transepithelial voltage completely. These data lead us to conclude that basolateral acidosis affects multiple transport pathways, and it inhibits mainly apical barium-sensitive potassium transport. Additionally, it inhibits apical sodium conductance, barium-insensitive potassium transport, and stimulates a ouabain-insensitive electrogenic transport pathway to some degree.
authors.affiliation: Department of Medicine, Jichi Medical School, Tochigi, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Tabei
authors.forename: S
authors.initials: S
authors.lastname: Muto
authors.forename: H
authors.initials: H
authors.lastname: Furuya
authors.forename: Y
authors.initials: Y
authors.lastname: Sakairi
authors.forename: Y
authors.initials: Y
authors.lastname: Ando
authors.forename: Y
authors.initials: Y
authors.lastname: Asano
mesh_terms: D000138:Acidosis / Q000378:metabolism*; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D004563:Electrochemistry; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials; D010042:Ouabain / Q000494:pharmacology; D010477:Perfusion; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011817:Rabbits; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
chemical_list: D001639:Bicarbonates; D015221:Potassium Channels; D010042:Ouabain; D012964:Sodium; D012413:Rubidium; D011188:Potassium