Andrographis paniculata (Ness) induces relaxation of uterus by blocking voltage operated calcium channels and inhibits Ca+2 influx

The possible relaxation of uterine smooth muscle by Andrographis paniculata dried extract via a blockade of voltage operated calcium channels was inve stigated in rats. Uterine horns pretreated with oestradiol were incubated i n Ca+2-free Jalon's solution and stimulated with KCI (20-60 mM) in order to produce depolarization of the membrane. The isometric contractile response to 1 mM or cumulative concentrations of CaCl2 were blockaded by 0.2, 0.4 a nd 0.8 mg/mL of A. paniculata. The maximum contractile response induced by acetylcholine was moderately antagonized by A. paniculata, The possible blo ckade of Ca+2 entry by A, paniculata was evaluated with Ca-45(+2) uptake in uterine rings incubated with free-Ca+2-Ringer's solution high in K+ (KCl 4 0 mM), The influx was completely blockaded with 0.4 mg/mL of A, paniculata. These results strongly suggest that A. paniculata blockades voltage operat ed calcium channels inhibiting the entry of Ca+2 from the external medium. Copyright (C) 2001 John Wiley & Sons, Ltd.