Tetrandrine, a calcium antagonist of Chinese herbal origin, interacts with vascular muscle α1-adrenoceptor

The effects of tetrandrine (TET) on the contractile responses of rat aortic rings and perfused rat mesenteric arteries to phenylephrine (PE) were investigated. TET inhibited the maximal contraction to PE in a concentration-dependent manner. TET significantly inhibited the transient contraction in Ca(2+)-free medium presumably due to release of intracellular Ca2+ after activation of alpha 1-adrenoceptors. However, it caused a stronger inhibition …