Comparative study of thrombolysis by high and low molecular weight urokinase in an in vitro perfusion system

Two urokinase preparations of different molecular weights were standardized against the International Reference Preparation for Urokinase and compared in an in vitro whole blood perfusion system using thrombi formed with whole blood and 125I-fibrinogen. Plasminogen was added to one group and normal saline to the other. Thrombolysis, as well as plasminogen and plasmin inhibitor levels were monitored over a 60 minute period following the addition of the urokinase to the perfusion mediums. There was a high correlation as well as no significant difference found between the percents lysis caused by the high and low molecular weight urokinase. Added plasminogen resulted in a rapid decrease of plasmin inhibitors in both urokinase groups. In the saline groups this decrease was highly negatively correlated with the percent lysis. It is concluded that both high and low molecular weight urokinase behave similarly in an in vitro whole blood thrombolytic perfusion system over the time period studied.