SOUTH-AMERICAN SNAKE-VENOMS AFFECTING HEMOSTASIS

The venom of the South American snakes, Bothrops, Crotalus and Lachesi s possess venom components which affect the haemostatic mechanism. The se components can interfere with blood coagulation and platelet functi on either by activation or inhibition. They are rich sources of serine proteinases called thrombin-like enzymes (TLEs) which induce direct c lotting of fibrinogen, and also metalloproteinases activators of proth rombin and Factor X. They are also rich in phospholipases which have a dual inhibitory action on blood coagulation factors and platelets; ho wever, the mechanism of action is still unclear, Among the platelet ac tivators, botrocetin from Bothrops jararaca venom is the most extensiv ely studied in the investigation of platelet function and von Willebra nd Factor abnormalities. RGD-containing polypeptides, platelet antagon ists found in Bothrops and Lachesis venoms are not only important as t ools for platelet studies but are also very promising candidates for r educing the risks of thromboembolic disease. Here some of the most imp ortant components in these venoms and the haemostatic alterations caus ed by them in reported cases of envenoming are described.