ACTION OF SNAKE-VENOM COMPONENTS ON THE HEMOSTATIC SYSTEM

Among the components in snake venom are a number which have profound e ffects (either stimulatory or inhibitory) on haemostatic mechanisms, i ncluding coagulation, fibrinolysis, platelet function and vascular int egrity. As a consequence, human victims of snakebite may suffer severe and sometimes fatal haemorrhagic and/or thrombotic sequelae. Many of these venom components have been isolated and their precise mechanisms of action established. Apart from direct fibrinolysins, procoagulants predominate, most of these exerting their effect late in the clotting cascade, activating factor X or prothrombin or directly converting fi brinogen to fibrin. Some of the procoagulants are, or have the potenti al to be, used as therapeutic agents. Some venom components have been put to use as laboratory reagents for diagnostic purposes or for chara cterising molecular defects of haemostasis, although because they ofte n have unphysiological actions, results must be interpreted with cauti on. These and other useful constituents e.g. protein C activator and p latelet aggregating agents are discussed.