The enzymatic dissolution of experimental arterial thrombi in the dog by trypsin, chymotrypsin and plasminogen activators.

A number of investigators have undertaken studies on the dissolution of intravascular thrombi and emboli by enzymes capable of effecting the dissolution of blood clots in vitro (1-4). Two types of approach have been used; the directintroduction of a proteolytic enzyme capable of digesting fibrin (2, 3), and activation of the naturally occurring proteolytic and fibrinolytic enzyme of mammalian plasma by the injection of a specific kinase (1). This latter approach is based on the observation that plasma contains a proenzyme termed plasminogen (5) or profibrinolysin (6), which, when activated, is converted to plasmin or fibrinolysin, a proteolytic enzyme with an affinity for fibrin (7). The action of plasmin is not limited to fibrin alone (8-11). The natural mechanisms for activation of plasminogen may be through blood (12) or tissue kinases (13, 14). The best known activator of human plasminogen is streptokinase, an extracellular hemolytic streptococcal product (8). Recent reports have appeared on the successful liquefaction of intravascular clots in rabbit ear veins by the intravenous infusion of large amounts of streptokinase (1); the lysis of venous clots in rabbits and dogs by the intravenous administration of large amounts of trypsin (2); and the dissolution of venous thrombi in rabbits and dogs by injections of purified human plasmin (previously activated in vitro by streptokinase) (3). It is the purpose of this report to describe the effects of the intravenous administration of trypsin,