The interaction of canrenone with the Na+,K+ pump in human red blood cells |
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Authors: | R P Garay J Diez C Nazaret G Dagher J P Abitbol |
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Institution: | (1) U7 INSERM/LA 318 CNRS, Necker Hospital, 161 rue de Sèvres, F-75015 Paris, France;(2) Theraplix Laboratories, 46-52 rue Albert, F-75013 Paris, France |
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Abstract: | Summary Canrenone inhibits 30–40% of ouabain-sensitive Na+ efflux in human red cells. Half-maximal inhibition was obtained with a canrenone concentration=86±37 mol/l (mean±SD of 13 experiments). The partial inhibition of the Na+,K+ pump appears to be mediated at the digitalis receptor site with an apparent dissociation constant (K
C)=200±130 mol/l (mean±SD). Further evidence suggesting that canrenone is a partial agonist at the digitalis receptor site was obtained by the observation that it decreases the apparent affinity of the Na+,K+ pump for external K+. However, in contrast to ouabain, canrenone decreases the apparent pump affinity for internal Na+.Our results show that, at physiological cell Na+ levels canrenone is able to enhance the inhibition of the Na+,K+ pump by low doses of ouabain. Conversely, in cells treated with high concentrations of cardiac glycosides (in which cell Na+ content increases), canrenone is able to restimulate the blocked pumps. |
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Keywords: | Canrenone Ouabain Aldosterone antagonists Diuretics Digitalis glycosides Na+ transport Na+ permeability Erythrocytes |
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