The thrombolytic activity of streptokinase in the rabbit.

The activity of streptokinase (SK) has been examined in a rabbit model of venous thrombosis. Significant thrombolysis was observed at low doses of SK without evidence of systemic activation of the fibrinolytic system. The origin of the specificity of SK-induced fibrinolysis in the rabbit was explored, using a chromogenic substrate coupled assay to measure the enhancement of plasmin generation in the presence of rabbit fibrin. The results obtained suggest that rabbit fibrin influences the fibrinolytic system at three points, viz: the assembly of an activator complex from rabbit plasminogen and SK; the activity of that activator complex towards further rabbit plasminogen; and the activity of the resulting rabbit plasmin in the presence of plasma inhibitors.