Studies on the calcium antagonistic action of tetrandrine: VI. Effects of tetrandrine on contractility of isolated rat uterus

Abstract

The isolated rat uterus contraction induced by oxytocin and Ca^{+ +} after high-K depolarization were markedly inhibited by tetrandrine (Tet). The depression was immediately reversed by addition of Ca⁺⁺ to the bath fluid. Tet and verapamil (Ver), which shifted the cumulative dose-response curves to the right and depressed the maximal responses to CaCl₂ acted as non-competitive antagonists. The oxytocin-induced Ca⁺⁺-dependent contractions were depressed by 4.8 and 30 μM Tet. Tet 30 μM also inhibited the Ca⁺⁺_o-dependent component of the contraction.

The effect of Ver on isolated rat uterus was stronger than that of Tet. But up to 0.05 μM, it showed no effect on Ca^{+ +}-dependent oxytocin contraction.

These results indicate that Tet is an effective Ca^{+ +}-antagonist very similar to Ver on isolated rat uteri.

Keywords

tetrandrine / iproveratril / calcium antagonist / oxytocin / isolated rat uterus

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