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 investigated in rats. Uterine horns pretreated with oestradiol were incubated in Ca +2 ‐free Jalon's solution and stimulated with KCl (20–60 m M ) in order to produce depolarization of the membrane. The isometric contractile response to 1 m M or cumulative concentrations of CaCl 2 were blockaded by 0.2, 0.4 and 0.8 mg/mL of A. paniculata . The maximum contractile response induced by acetylcholine was moderately antagonized by A. paniculata . The possible blockade of Ca +2 entry by A. paniculata was evaluated with 45 Ca +2 uptake in uterine rings incubated with free‐Ca +2 ‐Ringer's solution high in K + (KCl 40 m M ). The influx was completely blockaded with 0.4 mg/mL of A. paniculata . These results strongly suggest that A. paniculata blockades voltage operated calcium channels inhibiting the entry of Ca +2 from the external medium. Copyright © 2001 John Wiley & Sons, Ltd.