title: ENaC inhibition stimulates HCl secretion in the mouse cortical collecting duct. II. Bafilomycin-sensitive H+ secretion.
abstract: Epithelial Na(+) channel (ENaC) blockade stimulates stilbene-sensitive conductive Cl(-) secretion in the mouse cortical collecting duct (CCD). This study's purpose was to determine the co-ion that accompanies benzamil- and DIDS-sensitive Cl(-) flux. Thus transepithelial voltage, VT, as well as total CO2 (tCO2) and Cl(-) flux were measured in CCDs from aldosterone-treated mice consuming a NaCl-replete diet. We reasoned that if stilbene inhibitors (DIDS) reduce conductive anion secretion they should reduce the lumen-negative VT. However, during ENaC blockade (benzamil, 3 μM), DIDS (100 μM) application to the perfusate reduced net H(+) secretion, which increased the lumen-negative VT. Conversely, ENaC blockade alone stimulated H(+) secretion, which reduced the lumen-negative VT. Application of an ENaC inhibitor to the perfusate reduced the lumen-negative VT, increased intercalated cell intracellular pH, and reduced net tCO2 secretion. However, benzamil did not change tCO2 flux during apical H(+)-ATPase blockade (bafilomycin, 5 nM). The increment in H(+) secretion observed with benzamil application contributes to the fall in VT observed with application of this diuretic. As such, ENaC blockade reduces the lumen-negative VT by inhibiting conductive Na(+) absorption and by stimulating H(+) secretion by type A intercalated cells. In conclusion, 1) in CCDs from aldosterone-treated mice, benzamil application stimulates HCl secretion mediated by the apical H(+)-ATPase and a yet to be identified conductive Cl(-) transport pathway; 2) benzamil-induced HCl secretion is reversed with the application of stilbene inhibitors or H(+)-ATPase inhibitors to the perfusate; and 3) benzamil reduces VT not only by inhibiting conductive Na(+) absorption, but also by stimulating H(+) secretion.
authors.affiliation: Department of Medicine. Emory University School of Medicine, Atlanta, Georgia;
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nanami
authors.affiliation: Department of Medicine. Emory University School of Medicine, Atlanta, Georgia;
authors.forename: Vladimir
authors.initials: V
authors.lastname: Pech
authors.affiliation: Department of Medicine. Emory University School of Medicine, Atlanta, Georgia;
authors.forename: Yoskaly
authors.initials: Y
authors.lastname: Lazo-Fernandez
authors.affiliation: Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York; and Department of Medicine, Weill Medical College of Cornell University, New York, New York.
authors.forename: Alan M
authors.initials: AM
authors.lastname: Weinstein
authors.affiliation: Department of Medicine. Emory University School of Medicine, Atlanta, Georgia; Department of Physiology, Emory University School of Medicine, Atlanta, Georgia; smwall@emory.edu.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Wall
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D055724:Electrophysiological Phenomena / Q000187:drug effects; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006851:Hydrochloric Acid / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D018942:Macrolides / Q000494:pharmacology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D026941:Sodium Channel Blockers / Q000494:pharmacology*; D064506:Solute Carrier Family 12, Member 2 / Q000378:metabolism; D013267:Stilbenes / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000076988:Sulfate Transporters
chemical_list: D027321:Anion Transport Proteins; D002712:Chlorides; D018942:Macrolides; C578878:Slc12a2 protein, mouse; C494849:Slc26a4 protein, mouse; D026941:Sodium Channel Blockers; D064506:Solute Carrier Family 12, Member 2; D013267:Stilbenes; D000076988:Sulfate Transporters; C013407:benzamil; C057620:bafilomycin A; D000584:Amiloride; D006180:Proton-Translocating ATPases; D006851:Hydrochloric Acid
keywords: H+ secretion; chloride; pendrin