Abstract
The effects of sodium canrenoate (CRN), 0.5 to 1600 µg/ml, on isolated rat atria and ventricular strips and on isolated perfused hearts were studied. CRN produced a rapid, dose-dependent and reversible negative inotropic effect on isolated atria and ventricular strips. On perfused hearts, the effect was similar, although at low concentrations, the initial depression was sometimes followed by a small positive inotropic effect which could be related to the decrease in coronary resistance produced by CRN. CRN produced a rapid, reversible and dose-dependent increase in the amplitude and duration of the action potential plateau and reduced the rate of rise of the response. Abnormal rhythms were often diminished or suppressed by CRN. During CRN perfusion the inotropic effect of ouabain and various effects of acetylcholine (such as inotropic and chronotropic effects and action potential shortening) were decreased or suppressed. The CRN-induced lengthening of the action potential persisted during anoxia, cyanide, iodoacetate or ouabain perfusion. The uptake of 42K reversibly increased during CRN perfusion. In view of the electrophysiological results, CRN would appear to decrease potassium and sodium conductances of rat myocardium membranes, the latter effect being probably related to an increased inactivation of sodium conductance.
Footnotes
- Received May 31, 1972.
- Accepted June 6, 1974.
- © 1974 by The Williams & Wilkins Company