The anticoagulant effect of Bothrops castelnaudi snake venom (Castelnaud's pit viper)

An inhibitory effect of Bothrops castelnaudi venom was observed on the following systems: prothrombin time, activated partial thromboplastin time, thrombin time, thromboplastin generation time, activation of factor X by Russell's viper venom and Russell's viper venom activated factor X (factor Xa). This effect did not require previous incubation and was prevented by the addition of Bothrops-antivenom. The prolonged activated partial thromboplastin time was not shortened by increased phospholipid concentration (0.5-10 mg/ml), suggesting that the inhibitory effect is not due to an anti-phospholipid activity. No significant fibrinogenolytic activity was detected upon incubation of human fibrinogen with the venom, since physiological levels of thrombin-clottable material were still present. Compared to Bothrops jararaca venom, the proteolytic activity on casein and on azocoll was very low. Thrombin-induced clots of human plasma and fibrinogen were not lysed by the venom within 24 hr. The results indicate that the anticoagulant effect of Bothrops castelnaudi venom is exerted at least at two levels of the blood coagulation mechanism: (1) before prothrombin activation, by inhibiting factor X-activation and factor Xa activity; (2) by direct action on thrombin.