title: Na-independent Cl(-)-HCO3- exchange mediates recovery of pHi from alkalosis in guinea pig ventricular myocytes.
abstract: The pH-sensitive fluorescent indicator, carboxy-seminaphthorhodafluor 1 (SNARF 1) was used to assess the contribution of forward Na-independent Cl(-)-HCO3- exchange (1 external Cl- exchanged for 1 internal HCO3-) to intracellular pH (pHi) recovery from alkalosis in adult ventricular myocytes (guinea pig). Intracellular alkalosis was elicited by external application of the weak base, trimethylamine. In the absence of CO2-HCO3- (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-buffered solution) the initial rate of pHi recovery from alkalosis (pHi = 7.25-7.75) was slow and independent of pHi, yielding an apparent net HCO3- efflux of 0.36 +/- 0.11 mM/min. In CO2-HCO3(-)-buffered solution, the initial rate of pHi recovery and net HCO3- efflux were much faster and markedly increased by raising pHi. At pHi approximately 7.25, net HCO3- efflux was approximately 2 mM/min and rose to 9 mM/min at pHi approximately 7.6. 4,4'-Diisothiocyanostilbene-2,2'-disulfonic acid (0.4 mM) decreased net HCO3- efflux by 78.1 +/- 8.9% in CO2-HCO3(-)-buffered solution. Reduction in extracellular Cl- concentration from 135 to 20 mM markedly slowed the rate of pHi recovery from alkalosis and reduced net HCO3- efflux. pHi recovery from alkalosis was unaffected by removal of external sodium or exposure to 1 mM amiloride. These results indicate that forward Na-independent Cl(-)-HCO3- exchange mediates pHi recovery from alkalosis in guinea pig ventricular myocytes.
authors.affiliation: Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City 84112.
authors.forename: P
authors.initials: P
authors.lastname: Xu
authors.forename: K W
authors.initials: KW
authors.lastname: Spitzer
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000471:Alkalosis / Q000378:metabolism*; D000584:Amiloride / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D017920:Antiporters / Q000502:physiology*; D001578:Benzopyrans; D002021:Buffers; D027963:Chloride-Bicarbonate Antiporters; D005110:Extracellular Space / Q000378:metabolism; D005456:Fluorescent Dyes; D006168:Guinea Pigs; D006352:Heart Ventricles; D006863:Hydrogen-Ion Concentration; D008744:Methylamines / Q000494:pharmacology; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009284:Naphthols; D009994:Osmolar Concentration; D012235:Rhodamines; D012964:Sodium / Q000378:metabolism*
chemical_list: D017920:Antiporters; D001578:Benzopyrans; D002021:Buffers; D027963:Chloride-Bicarbonate Antiporters; D005456:Fluorescent Dyes; D008744:Methylamines; D009284:Naphthols; D012235:Rhodamines; C068301:carboxy-seminaphthorhodaminefluoride; D000643:Ammonium Chloride; D000584:Amiloride; D012964:Sodium; C023336:trimethylamine; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid