Kinetics of urokinase-induced thrombolysis in a biphasic in vitro system

The role and effect of added lys-plasminogen (lys-PLG) on urokinase-induced thrombolysis in an in vitro biphasic system were investigated. The kinetics of lysis of whole blood thrombi was followed in perfusion mediums of normal plasma, PLG-deficient plasma and normal saline using a high and a low concentration of urokinase (UK). The lysis of standard whole blood thrombi in whole blood perfusion mediums to which had been added UK alone or UK plus lys-PLG was compared to whole blood thrombi enriched with lys-PLG by incorporation during thrombus formation or by adsorption during perfusion. In addition, the kinetics of lysis of PLG-deficient fibrin thrombi perfused in PLG-deficient plasma or normal saline was studied when lys-PLG had been added to the thrombus, to the perfusion medium or to both thrombus and medium. In PLG-deficient plasma from which plasmin inhibitors had not been removed, thrombolysis was minimal even at a high concentration of UK. This effect could be neutralized, and to some extent, regulated, by lys-PLG enrichment of the medium. Both PLG-incorporated and PLG-adsorbed whole blood thrombi gave initial and sustained acceleration of UK-induced lysis in comparison with standard nontreated thrombi. It is concluded that in a blood-thrombus biphasic thrombolytic system induced by UK, there is interaction between the phases, and that PLG in both phases influences thrombolysis.