Non Effectiveness of Ouabain and Decrease in Na⁺/K⁺ -ATPase Affinity for Ouabain in Failing Rabbit Heart

Abstract

Impaired mechanical perfomance is me usual cause of Congestive Heart Failure (CHF) (2,10). For this reason, digitalis drugs are still the oldest compounds to treat CHF and still remain the mainstay of treatment despite the advent of new inotropes and vasodilators (9). Multiple changes are described in the failing myocardium such as a downregulation of β adrenoreceptors, a deficient production in cAMP, a decrease in the function of the sarcoplasmic reticulum, an inhibition in the Na⁺/Ca^{+ +}-exchange leading to excessive calcium accumulation (2,5,6,10). Several studies have examined the Na⁺/K⁺-pump in failing hearts but their conclusions are divergent (1,2,7,11). Some of these discrepancies could be due to the experimental model of heart failure, the utilized mammalian species and enzyme assay using pure sarcolemmal membrane fractions with low recovery.