Summary
1. A sensitive test system has been described whereby the respective fibrinolytic
and fibrinogenolytic effects of plasminogen activators and proteolytic enzymes in
plasma may be quantitated separately by use of isotopically labeled substrates.
2. Plasminogen activators in the plasma-clot system were demonstrated to lyse more
fibrin per unit fibrinogen lysed than either plasmin or trypsin. No evidence was obtained
to suggest the formation of a plasmin-antiplasmin complex with special “fibrinolytic”
porperties.
3. Comparison of the effects of streptokinase and urokinase in plasma revealed discrete
differences in the ratio of their fibrinolytic-fibrinogenolytic activities.