Effect of five Thai snake venoms on coagulation, fibrinolysis and platelet aggregation.

The effects of five Thai snake venoms--Malayan pit viper--MPV (Ancistrodon rhodostoma); Russell's viper--RVV (Vipera russelli); cobra--CV (Naja naja); king cobra--KCV (Naja hannah) and banded krait--BKV (Bungarus fasciatus)--on blood coagulation fibrinolysis and platelet aggregation were studied. MPV has strong thrombin-like coagulant action. RVV has activating effect most probably on factor X. Other three venoms--CV, KCV and BKV have been shown to be anti coagulant, on both intrinsic and extrinsic clotting pathways. MPV has strong lytic activity on normal euglobulin clot while CV has mild accelerating action. RVV and BKV inhibit the lysis of euglobulin clot. KCV has no effect on fibrinolysis. None of the five venoms has direct aggregating activity on platelets. All except MPV inhibit ADP-induced platelet aggregation at their higher concentrations.