Enhancement of the thrombolytic efficacy of prourokinase by lys-plasminogen in a dog model of arterial thrombosis

Current findings suggest that the efficacy of thrombolytic therapy may be limited by the availability of active forms of plasminogen at the thrombus site (1, 2). The purpose of this study was to determine if the systemic administration of 0.5 mg kg^-1 glu-plasminogen (glu-plg) or 0.5 mg kg^-1 lysplasminogen (lys-plg) could safely increase the efficacy of a single intravenous bolus injection of 50,000 U kg^-1 prourokinase (proUK) in a dog model of arterial thrombosis. Thrombolysis was measured by monitoring the continuous decrement of ¹²⁵I-gamma emissions from a radiolabeled thrombus. Reflow was evaluated by direct visual examination. Forty dogs (mean wt 10.3 ± 2 kg) were randomly sorted into 4 groups of 10 each. The dogs in each group were given either saline plus saline, saline plus proUK, glu-plg plus proUK, or lys-plg plus proUK 60 minutes after formation of an occlusive arterial thrombus. Ninety minutes after drug administration the dogs receiving saline plus proUK, glu-plg plus proUK, and the lys-plg plus proUK showed greater thrombolysis (41%, 43%, and 66%, respectively) than the control (saline plus saline) group (15%, P < 0.01). The lys-plg plus proUK treatment caused greater lysis than the saline plus proUK or the glu-plg plus proUK treatment (P < 0.05). All of the dogs ( 10 10) receiving lys-plg plus proUK had patent vessels at the end of the 90 minute monitoring period, whereas only 4 10 and 5 10 vessels were patent in the saline plus proUK and glu-plg plus proUK groups, respectively. None of the dogs in the saline plus saline group had patent vessels. No significant changes were observed in the various coagulation parameters tested for any of the 4 treatment groups. The results show that lys-plg can safely increase the thrombolytic efficacy of proUK.