Effects of tetrandrine on cardiovascular electrophysiologic properties.

Tetrandrine (Tet) is one of the best characterized Ca2+ channel blocker of plant origin. It can affect cardiovascular electrophysiologic properties in following field: inhibit the contractility, +/-dt/dpmax, and automaticity of myocardium, prolong the FRP, and exert concentration-dependent negative inotropic and chronotropic effects without altering cardiac excitability. Tet directly blocks both T-type and L-type calcium current in ventricular cells and vascular smooth muscle cells, but it does not shift the I-V relationship curve of ICa. All its effects would be beneficial in the treatment of angina, arrhythmias, and other cardiovascular disorders. Tet also directly inhibits the activity of BKCa channel in endothelial cell line and also inhibits Ca2+-release-activated channels in vessel endothelial cells, which might significantly contribute to the change of endothelial cell activity.