Cepharanthine, a biscoclaurine alkaloids which interact with biomembranes, has been found to inhibit platelet aggregation. The effects of this drug on morphological and physiochemical phenomena following collagen-induced platelet stimulation were investigated. In the presence of cepharanthine, stimulated platelets became spherical, but did not form pseudopoda , nor did they become aggregated. Physiochemical reactions such as accelerated oxygen consumption, release of membrane-bound Ca2+, release of Ca2+ into the extracellular medium and deporalization of the membrane potential were all inhibited by cepharanthine. Using D,L-dipalmitoyl phosphatidylcholine liposomes as the substrate, cepharanthine was shown to inhibit phospholipase A2 activity. These results suggest that the changes in the membrane following the interaction of collagen with its receptor are important for platelet activation. Cepharanthine may inhibits these membrane state changes, thus blocking all subsequent reactions.</p
