CROTOXIN INDUCES AGGREGATION OF HUMAN WASHED PLATELETS

Crotoxin, the main toxic component isolated from the venom of the Sout h American rattlesnake Crotalus durissus terrificus, is a reversible p rotein complex composed of a non-toxic non-enzymatic acidic polypeptid e (crotapotin) and a toxic basic phospholipase A(2) (PLA(2)). In this study, we have evaluated the ability of crotoxin to induce aggregation in human washed platelets. Human washed platelet aggregation was moni tored in a Payton aggregometer and thromboxane B-2 (TXB(2)) release me asured by direct radioimmunoassay (RIA). Crotoxin (15-50 mu g/ml) prod uced dose-dependent and irreversible human washed platelet aggregation , which was inhibited by pre-incubation of the platelets with sodium n itroprusside (50-500 mu M) or iloprost (8-80 nM). Crotoxin also induce d TXB, release (207 +/- 8 ng/ml, n = 6), and although indomethacin sig nificantly reduced the release of TXB, (to 23.5 +/- 5 ng/ml, P < 0.001 , n = 6), it did not inhibit crotoxin-induced aggregation. Our results clearly demonstrate that crotoxin induces human washed platelet aggre gation and that this phenomenon is independent of the formation of pro -aggregatory arachidonic acid metabolites.