SOUTH-AMERICAN SNAKE-VENOMS AFFECTING HEMOSTASIS

The venom of the South American snakes, Bothrops, Crotalus and Lachesis possess venom components which affect the haemostatic mechanism. These components can interfere with blood coagulation and platelet function either by activation or inhibition. They are rich sources of serine proteinases called thrombin-like enzymes (TLEs) which induce direct clotting of fibrinogen, and also metalloproteinases activators of prothrombin and Factor X. They are also rich in phospholipases which have a dual inhibitory action on blood coagulation factors and platelets; however, the mechanism of action is still unclear, Among the platelet activators, botrocetin from Bothrops jararaca venom is the most extensively studied in the investigation of platelet function and von Willebrand Factor abnormalities. RGD-containing polypeptides, platelet antagonists found in Bothrops and Lachesis venoms are not only important as tools for platelet studies but are also very promising candidates for reducing the risks of thromboembolic disease. Here some of the most important components in these venoms and the haemostatic alterations caused by them in reported cases of envenoming are described.