Effect of oxyphenamone on sodium and calcium channels of guinea pig myocardial cells

AimTo investigate the mechanism of the positive inotropic effect of oxyphenamone． MethodsWith the patch clamp technique and whole cell recording, the sodium and L type calcium currents of myocytes isolated from ventricular myocardium of adult guinea pigs were studied． Results5-50 μmol·L^-1oxyphenamone not only significantly inhibited Na+ current， but also promoted the process of inactivation and prolonged the recovery time of the inactivation． The action of oxyphenamone on L type calcium channel was dual． The inward calcium current was increased with 2-10 μmol·L^-1oxyphenamone but decreased when the concentration of the drug was elevated to 20-50 μmol·L^-1 ． ConclusionThe mechanism of the positive inotropic effect of oxyphenamone is neither due to the activation of sodium channel nor entirely depending upon the activation of L type calcium channel． The effects of inhibiting sodium current and， at a high concentration， blocking L type calcium current suggest that oxyphenamone may have an antiarrhythemia action．