The effect of the fibrinolytic enzyme Flla from Agkistrodon acutus venom on acute pulmonary thromboembolism

Aim： To evaluate the effects of the fibrinolytic enzyme Flla from Agkistrodon acutus venom on acute pulmonary thromboembolism （APT） in animal models. Methods： Both rabbit and dog APT models were used. For the rabbit APT model, the thrombi weight before and after administration was measured. Central venous pressure （CVP） and mean arterial pressure （MAP） were measured before and 15, 30, 60, and 120 min after the injection of the blood clot. Partial thromboplastin time （APTT）, prothrombin time （PT）, platelet count, and fibrinogen concentration were measured using auto analyzers. Plasminogen activity was measured based on chromogenic substrates. In the dog APT model, pulmonary blood flow was recorded using pulmonary angiography. Results： Intravenous administration of Flla （0.1-5.0 mg/kg） improved the APT-induced hemodynamic derangements and reduced thrombi weight. The angiography evidence also showed that the pulmonary emboli had almost disappeared after Flla infusion. Flla （0.1, 0.5, or 1.0 mg/kg） did not impair the coagulation pathways, although very high doses of FII, （5.0 mg/kg） could stimulate the production of plasminogen and result in impairment of the pathways. Conclusion： Flla could effectively protect against APT via degradation of thrombi with less activation of plasminogen, and may provide a novel fibrinolytic enzyme for targeting the main pathological processes of the disease.