Studies on the calcium antagonistic action of tetrandrine: IX. Effects of tetrandrine on action potential and contraction of isolated guinea pig papillary muscles

Abstract

The effects of tetrandrine (Tet) on action potential and contraction were studied in isolated guinea pig papillary muscles in normal and K⁺-rich Tyrode’s solution.

Tet produced concentration-dependent negative inotropic effect and shortened APD₂₀ (action potential duration) and APD₉₀, while resting potential and amplitude of the action potential were not affected. Thus, an excitation-contraction uncoupling was revealed. Tet decreased the amplitude of Ca⁺⁺-mediated slow action potential induced by high K⁺. These results are in contrast with those of quinidine but are consistent with those of slow channel blockers.

Keywords

tetrandrine / quinidine / papillary muscle / action potential / contractile force / extracellular K⁺ / excitation-contraction coupling

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