TY - JOUR AU - Jin Man-wen AU - Fang Da-chao AU - Jiang Ming-xing PY - 2016 TI - Influence of tetrandrine on positive inotropic action of isoproterenol and CaCl2 and on excitation-contraction coupling in isolated cat papillary muscles JF - Acta Pharmacologica Sinica; Vol 3, No 2 (June 1982): Acta Pharmacologica Sinica Y2 - 2016 KW - N2 - The effects of tetrandrine, verapamil, propranolol and practolol on isoproterenol dose-response relationships and the influence of tetrandrine, verapamil and nifedipine on calcium dose-response relationships and on excitation-contraction coupling were investigated on isolated cat papillary muscles. Propranolol and practolol competitively antagonized isoproterenol. Tetrandrine and verapamil also antagonized isoproterenol but in a non-competitive manner. Tetrandrineļ¼Œverapamil and nifedipine shifted calcium dose-response curves to the right, and acted as non-competitive antagonists of calcium, as a plot of log (x-1) vs -log [B] resulted in straight lines with slopes of -0.43, -0.55 and -0.42, respectively. Tetrandrine, verapamil and nifedipine resulted in excitation-contraction uncoupling. It was suggested that tetrandrine inhibited the inward diplacement of calcium through the voltage-dependent channel. The results support our speculation that tetrandrine is a calcium antagonist of plant origin. UR - http://www.chinaphar.com/article/view/4545