A New Method for the Determination of Antiplasmin and Antiactivator Activity in Plasma. The Role of these Inhibitors in Controlling the Lysis of Fibrinogen and Fibrin

In order to evaluate the effect of plasma inhibitors on the lysis of fibrinogen (F) and fibrin (f) by UK and an activator derived from euglobulin, agarose (1%) plates in borate buffer (pH 7.7) containing human F (0.1%) were prepared. Fibrinolysis was measured after incubation (18h., 37°C) on plates clotted with Arvin (10u.). Fibrinogenolysis was measured using unclotted plates to which Arvin and EACA (0.01M) were added after incubation with the activators. Lytic activity was determined by measuring the clear circular zone around the wells containing the activators. In both the F and f plates, a linear relation between lysis zones and UK concentrations (0-100u/ml) was found. Inhibitors in human plasma (HP) were evaluated by incubating (15 min.) activators with HP prior to their application to the plates. This resulted in a slight (10-20%) reduction in lysis on the f plates and total inhibition of lysis on the F plates. By contrast, when plasmin was mixed with HP, the lysis zones on the F and f plates were identical. It was concluded that an antiactivator rather than an antiplasmin is responsible for the inhibition of F-lysis. These F and f agarose plates provide a practical means for the semiquantitative determination of antiactivators and antiplasmins in patient plasma.