Ouabain sensitivity of Rb+ uptake in canine Purkinje fibre and ventricular muscle.

Ouabain inhibitable active Rb+ uptake was compared in canine Purkinje fibre and the left ventricular muscle to define the possible difference in electrophysiological sensitivity to ouabain in the two tissues. Ouabain inhibitable, active uptake of Rb+ was calculated from the difference between total Rb+ uptake assayed in the absence of ouabain and nonspecific Rb+ accumulation assayed in the presence of 10(-4) mol/l ouabain. A similar degree of active Rb+ uptake was inhibited by ouabain in both Purkinje fibre and the left ventricular muscle from the same animal, even though the Purkinje fibre took up more 86Rb+ than the ventricle. The specific tissue binding of ouabain in vitro was also not significantly different in the functionally different two tissues. It is concluded that there is no differential ouabain sensitivity of Rb+ uptake in canine Purkinje fibre and ventricular muscle.