Differential Inhibition with Antifibrinolytic Agents of Staphylokinase and Streptokinase Induced Clot Lysis

The inhibitory effects of antifibrinolytic amino acids on clot lysis induced with recombinant staphylokinase (SakSTAR) or with streptokinase (SK) were evaluated in a human plasma milieu in vitro and in a hamster pulmonary embolism model in vivo. Addition of tranexamic acid to a system composed of 60 microliters 125I-fibrin-labeled plasma clots submerged in 0.5 ml human plasma, caused dose-dependent inhibition of lysis; complete lysis in 120 min required 30 nM SakSTAR or 100 nM SK and was reduced to 50% with 0.015 mM or with 0.07 mM tranexamic acid, respectively. Aprotinin also produced dose-dependent inhibition; lysis with SakSTAR or with SK was reduced to 50% of the control value with 8 KIU/ml or with 10 KIU/ml aprotinin, respectively. Thus, in human plasma in vitro the antifibrinolytic potency of tranexamic acid was 5-fold higher towards SakSTAR than towards SK, whereas that of aprotinin was comparable towards both agents. In hamsters with pulmonary embolism given 0.063 mg/kg SakSTAR or 0.20 mg/kg SK over 30 min, the antifibrinolytic potency of tranexamic acid, administered as a single bolus injection or as a bolus injection followed by continuous infusion, was 8- to 10-fold higher towards SakSTAR than toward SK (50% reduction of clot lysis with SakSTAR at 12.5 mg/kg, as compared to 100-150 mg/kg with SK). In contrast, aprotinin was equipotent towards SakSTAR and SK (50% reduction of clot lysis with 2,000 to 2,700 KIU/kg).(ABSTRACT TRUNCATED AT 250 WORDS)