[Experimental animal research on the thrombolytic effect of acyl-plasmin]

Plasmin was acylated by reaction with benzoic acid or p-chlorobenzoic acid p'-amidinophenyl ester. Enzymatically inactive acyl-plasmin is reactivated in buffer (pH 7.5) with a half-life of 22 min (benzoyl-plasmin) and 9 min (p-chlorobenzoyl-plasmin), respectively. Plasmin is rapidly inactivated in plasma by naturally occurring plasma inhibitors so that also upon incubation of acyl-plasmin in plasma only low enzymatic activity is detectable. Following high doses of plasmin fibrinogenolysis typical of nonspecific proteolysis occurs in vivo but no fibrinolytic effects is demonstrable. On the other hand, acyl-plasmins are able either to prevent microthrombosis in the lungs induced by infusion of thrombin or to achieve repatency of the microvasculature after the onset of microthrombosis.