Purification and characterization of a platelet aggregation inducer from Calloselasma rhodostoma (Malayan pit viper) snake venom.

A potent platelet aggregation inducer was purified from Calloselasma rhodostoma snake venom by Sephadex G-75, CM-Sephadex C-50 and Sephacryl S-300 column chromatography. It was homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with a molecular weight estimated to be 28,160 +/- 1280. It was devoid of phospholipase A2, fibrino(geno)lytic and thrombin-like activities. The venom inducer elicited platelet aggregation and the serotonin release reaction in rabbit platelet-rich plasma and platelet suspension. Exogenous calcium was required for its platelet activation. Creatine phosphate/creatine phosphokinase and indomethacin did not inhibit the venom inducer-induced aggregation and release reaction. Mepacrine and verapamil preferentially inhibited aggregation, while PGE1 completely blocked both aggregation and release reaction. It is concluded that the venom inducer activates platelets through the activation of endogenous phospholipase A2 or C, leading to intracellular calcium mobilization, but independent of the ADP release reaction or thromboxane A2 formation.