Dissolution of thrombi by tissue plasminogen activator, urokinase and streptokinase in an artificial circulating system

The ability of porcine tissue plasminogen activator, urokinase and streptokinase to dissolve whole blood clots has been compared in an artificial circulating system, the Chandler loop. On a molar basis the tissue activator was more effective in lysing both partially and totally crosslinked thrombi than urokinase or streptokinase. The latter drugs required 30–50 times higher concentrations to achieve a fibrinolytic response, similar to that of tissue activator. As demonstrated by analysis of fibrinogen, α 2-antiplasmin and plasmin-α 2-antiplasmin complex there was no activation of plasminogen in plasma by the tissue activator in the absence of fibrin. Both urokinase and streptokinase gave under the same conditions rise to a significant dose dependent fibrinogenolysis. In the presence of fibrin, tissue activator induced a weak fibrinogenolysis (about 20%) in plasma, whereas both urokinase and streptokinase caused a much higher degree of fibrinogenolysis (50 and 60 % respectively).