On the interaction between dextran and the primary fibrinolysis inhibitor α2-antiplasmin

Abstract The mechanism underlying the effect of dextran on the lysis of plasma clots was studied. With the aid of 125 I-plasminogen, the formation of radiolabelled derivatives of urokinase-induced plasminogen activation was followed in clotted plasma. The activation was enhanced by the presence of dextran, but the rate of formation of the complex between plasmin and α 2 -antiplasmin was not. By measuring the amount of plasmin activity remaining after addition of plasmin and α 2 -antiplasmin to clots or fibrinogen solutions, it was found that in purified fibrin clots the α 2 -antiplasmin activity was impaired in the presence of dextran. In fibrinogen solutions dextran appeared to have no effect on the α 2 -antiplasmin activity. It is concluded that two different mechanisms are involved in the dextran-induced improvement of plasma clot lysis - an increased plasminogen activation rate and decreased α 2 -antiplasmin activity. The latter effect is apparently dependent on the morphologically different type of fibrin formed in the presence of dextran.