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The effect of ouabain on intracellular activities of K+, Na+, Cl−, H+ and Ca2+ in proximal tubules of frog kidneys
Authors:W. Wang  G. Messner  H. Oberleithner  F. Lang  P. Deetjen
Affiliation:(1) Physiologisches Institut der Universität Innsbruck, Fritz-Pregl-Strasse 3, A-6010 Innsbruck, Austria;(2) Physiologisches Institut der Universität Würzburg, Röntgenring 9, D-8700 Würzburg, Federal Republic of Germany
Abstract:Using conventional and ion selective microelectrodes, the effect of ouabain (10–4 mol/l) on peritubular cell membrane potential (PDpt), on intracellular pH (pHi) as well as on the intracellular ion activities of Cl (Cli), K+ (Ki+), Na+ (Nai+) and Ca2+ (Cai2+) was studied in proximal tubules of the isolated perfused frog kidney. In the absence of ouabain (PDpt=–57.0±1.9 mV), the electrochemical potential difference of chloride (apparent {ie6-1} and of potassium {ie6-2} is directed from cell to bath, of H+ {ie6-3}, of Na+ {ie6-4} and of Ca2+ {ie6-5} from bath to cell. Ouabain leads to a gradual decline of PDpt, which is reduced to half (PDpt, 1/2) within 31±4.6 min (in presence of luminal glucose and phenylalanine), and to a decline of the absolute values of apparent {ie6-6}, of {ie6-7}, {ie6-8} and {ie6-9}. In contrast, an increase of {ei6-10} is observed. At PDpt, 1/2 apparent Cli increases by 6.2±1.0 mmol/l, pHi by 0.13±0.03, Cai2+ by 185±21 nmol/l, and Nai+ by 34.2±4.6 mmol/l, whereas Ki+ decreases by 37.7±2.2 mmol/l. The results suggest that the application of ouabain is followed by a decrease of peritubular cell membrane permeability to K+, by an accumulation of Ca2+, Na+ and HCO3- in the cell and by a dissipation of the electrochemical Cl gradient.Supported by Österr. Forschungsrat, Proj. No. 4366
Keywords:Ouabain  Frog kidney  Proximal tubule  Ion sensitive microelectrodes  Na+/K+ pump  Intracellular K+, Na+, Cl  , pH, Ca2+
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