Andrographis paniculata (Nees) selectively blocks voltage-operated calciumchannels in rat vas deferens

The possible blockade of voltage-operated calcium channels (VOCs) by Androg raphis paniculata dried extract in vas deferens smooth muscle was investiga ted in rats. The tissues were incubated in Ca2+-free Kreb's solution and st imulated with KCl (40 mM) to produce depolarisation of the membrane. The is ometric contractile response to cumulative concentrations of CaCl2 was effe ctively blockaded by 0.2 and 0.4 mg/ml A. paniculata. In other experiments, the maximum contractile response induced by norepinephrine was not antagon ised by 0.2, 0.4 or 0.8 mg/ml A. paniculata. The possible blockade of Ca2entry by A. paniculata was evaluated with Ca-45(2+) uptake in vas deferens treated with reserpine (5 and 2.5 mg/kg) 48 and 24 h before the experiments . Epididymal segments were incubated with Ca2+-free Kreb's solution with KC l, 25 and 50 mM. The influx was completely blockaded with 0.4 mg/m A. panic ulata. These results suggest that A. paniculata selectively blockades VOCs, hence inhibiting the Ca-45(2+) influx. (C) 2000 Elsevier Science Ireland L td., All rights reserved.