Mechanism of Positive Inotropic Effect of Vincanine on Cardiac Muscle Contraction Activity

In the present study, the dose-dependent effect of the alkaloid vincanine on the contractile activity of rat heart papillary muscle was investigated and it was found to increase the force of muscle contraction at all concentrations. The half-maximal inotropic effect concentration (ED50) of vincanine was 21.8 μM, respectively. Studies of the effect of this alkaloid on the cardiomyocyte Na+-channel in the presence of its blocker lidocaine showed that the positive inotropic effect of vincanine does not involve the Na+-channel. When studying the effect of vincanine on Сa2+L-channels in the presence of nifedipine (IC50=0.01 μM), the positive inotropic effect of vincanine (50 μM) alkaloid was partially reduced. In general, it was found that the positive inotropic effect of vincanine on the force of papillary muscle contraction is partially mediated by Сa2+L-channels and mainly Na+/Сa2+ exchange.