INFLUENCE OF ZINC SULFATE ON MYOCARDIAL SLOW RESPONSE ELECTRICAL ACTIVITY AND OUABAIN INDUCED OSCILLATORY AFTERPOTENTIAL

The action of ZnSO₄ (0.1～0.3 mmol) on the slow response action potentials induced by high concentration K⁺ (25 mmol) was observed on isolated guinea pig papillary muscles. APA and V_max of the slow response action potentials were decreased. APD₅₀ and APD₉₀ were prolonged significantly. ZnSO₄ (0.1～0.3 mmol) inhibited the automaticity of the isolated rabbit sinoatrial node preparations. The sinus rate decreased (P<0.01). APA of the rabbit sinoatrial node was reduced, APD₉₀ prolonged, while SP₀ and SP₄ were decreased. Zinc sulfate (0.1 mmol) inhibited the guinea pig papillary muscle oscillatory afterpotential induced by ouabain (0.4 μmol). It increased the threshold concentration of ouabain necessary for inducing oscillatory afterpotential. The results suggest that ZnSO₄ inhibited myocardial slow response electrical activity.