THE ANTIPLATELET AGGREGATORY ACTIVITY OF ACACIA-NILOTICA IS DUE TO BLOCKADE OF CALCIUM INFLUX THROUGH MEMBRANE CALCIUM CHANNELS

1. The extract of Acacia nilotica (A. nilotica) blocked platelet aggre gation mediated by platelet agonists, arachidonic acid (0.75 mM), ADP (4.3 mu M), platelet activating factor (800 nM) and collagen (638 nM) in a dose-dependent manner. 2. The extract (0.21-1.4 mg/ml) blocked th e platelet aggregation induced by Ca2+ ionophore, A-23187 (6 mu M), in a dose-dependent manner, indicating that the Ca2+ influx is involved in aggregation. 3. The plant extract also inhibited aggregation in pla telets pretreated with phorbol, 12-myristate, 13-acetate (196 nM) alon e or in combination with ADP (4.3 mu M), indicating an effect on prote in kinase C. 4. These results indicate that the antiplatelet aggregato ry activity of the extract of A. nilotica is mainly due to blockade of Ca2+ channels, although evidence also suggests the involvement of pro tein kinase C. GEN PHARMAC 29;2:251-255, 1997. (C) 1997 Elsevier Scien ce Inc.