[Ouabain and intracellular potassium activity in the papillary muscle of the rabbit]

Ionic activity on both sides of the cardiac cell membrane is an essential parameter for determining the mechanism responsible for the positive inotropic effect of cardiotonic glucosides. The intracellular activity of K (aiK) was therefore measured using selective microelectrodes, in the papillary muscles of a rabbit, for both a low concentration (10(-8) M) and a toxic concentration (10(-6) M) of ouabain. The ouabain at low concentration (10(-8) M) had no significant effect with respect to aiK, the values derived with and without ouabain being 85.4 mequiv./L and 84.2 mequiv./L respectively. The use of selective microelectrodes for measuring K, paired with a microelectrode filled with KC1, made it possible to study aiK in terms of time in the presence of a toxic concentration of ouabain (10(-6) M). In such a case, ouabain results in a reversible lessening of aiK.