Electrophysiologic and inotropic effects of O-benzyl-phosphocreatine in rabbit myocardium.

O-benzyl-phosphocreatine-Na (BPC) applied in superfusion increased the action potential amplitude and isometric tension in the isolated sinus node strips, atrial trabeculae and papillary muscles. BPC enhanced the slope of the slow diastolic depolarization evoking the positive chronotropic effect. The drug prolonged the action potential duration in the atrial and ventricular cells. BPC exerted similar effects during hypoxia and cyanide superfusion in the working myocardium. On the other hand, phosphocreatine as well as O-benzyl-phosphoglycocyamine added to the superfusion fluid were ineffective. BPC increased also the ATP content of the superfused contracting atrial trabeculae. These results suggest that BPC crosses the sarcolemma, elevates the ATP content, and thereby it increases the slow inward and can serve as an additional source of the metabolic energy in the cardiac cells.