Synergistic Effect on Thrombolysis of Sequential Infusion of Tissue-Type Plasminogen Activator (t-PA) Single-Chain Urokinase-Type Plasminogen Activator (scu-PA) and Urokinase in the Rabbit Jugular Vein Thrombosis Model

Summary

In a quantitative model of thrombolysis, consisting of rabbits with a ¹²⁵T-fibrin labeled blood clot in the jugular vein, simultaneous intravenous infusion over 4 hours of t-PA and scu-PA or of t-PA and urokinase had a significantly greater (p <0.01) thrombolytic effect than could be anticipated on the basis of the added effects of each agent alone. In order to further investigate the mechanism of this in vivo synergism, recombinant t-PA (rt-PA) and scu-PA in synergistic amounts were infused: 1) simultaneously over 4 hours, 2) rt-PA over 1 hour, then 15 min later scu-PA over 2 hours and 3) scu-PA over 1 hour, then 15 min later rt-PA over 2 hours. Simultaneous infusion of 0.1 mg/kg rt-PA and 0.2 mg/kg scu-PA gave 48°2 percent thrombolysis (mean ° SEM, n = 5) and of 0.2 mg/kg rt-PA and 0.4 mg/kg scu-PA 67°5 percent (n = 5). When these infusions were given sequentially, rt-PA followed by scu-PA gave 32 °5 (n = 4) and 49 °8 (n = 4) percent lysis, but scu-PA followed by rt-PA yielded only 14° 1 (n = 4) and 21 ° 1 (n = 4) percent lysis, indicating that synergism occurs when rt-PA is followed by scu-PA but not when scu-PA is followed by rt-PA. In order to investigate the hypothesis that rt-PA predigests the clot resulting in more efficient plasminogen activation by scu-PA at the clot surface, partial thrombolysis was induced by injection of urokinase. Subsequent infusion of 0.4 mg/ kg of scu-PA did however not result in more thrombolysis than expected for additive effects. Infusion of 0.5 mg/kg of urokinase followed by 0.1 mg/kg rt-PA was not synergistic (24 °3 percent lysis, n = 3) whereas lysis by rt-PA followed by urokinase was 34°3 percent (p <0.1, n = 3).

Sequential therapy with rt-PA followed by scu-PA might constitute an alternative to simultaneous infusion of synergistic thrombolytic agents.

Keywords

Thrombolysis - t-PA - scu-PA - Urokinase - Synergism

• References

• 1 Collen D. Report of the Meeting of the Subcommittee on Fibrinolysis, San Diego, CA, USA, July 13, 1985. Thromb Haemostas 1985; 54: 893
• 2 Hoylaerts M, Rijken DC, Lijnen HR, Collen D. Kinetics of the activation of plasminogen by human tissue plasminogen activator. Role of fibrin. J Biol Chem 1982; 257: 2912-2919
• 3 Lijnen HR, Zamarron C, Blaber M, Winkler ME, Collen D. Activation of plasminogen by pro-urokinase. I. Mechanism. J Biol Chem 1986; 261: 1253-1258
• 4 Collen D, De Cock F, Dcmarsin E, Lijnen HR, Stump DC. Absence of synergism between tissue-type plasminogen activator (t-PA), single chain urokinase-type plasminogen activator (scu PA) and urokinase on clot lysis in a plasma milieu in vitro. Thromb Haemostas 1986; 56: 35-39
• 5 Guiewich V, Pannell R. A comparative study of the efficacy and specificity of tissue plasminogen activator and pio-uiokinase: demon stration of synergism and of different thresholds of non-selectivity. Thromb Res 1986; 44: 217-228
• 6 Collen D, Stassen JM, Stump DC, Verstraete M. Synergism of thrombolytic agents in vivo. Circulation 1986; 74: 838-842
• 7 Collen D, Stump DC, Van de Werf F. Coronary thrombolysis in patients with acute myocardial infarction by intravenous infusion of synergistic thrombolytic agents. Am Heart J 1986; 112: 1083-1084
• 8 Collen D, Van de Werf F. Coronary arterial thrombolysis with low dose synergistic combinations of recombinant tissue-type plasminogen activator (rt-PA) and recombinant single chain urokinase-type plasminogen activator (rscu-PA) for acute myocardial infarction. Am J Cardiol. (in press)
• 9 Collen D, Stassen JM, Verstraete M. Thrombolysis with human extrinsic (tissue-type) plasminogen activator in rabbits with experimental jugular vein thrombosis. Effect of molecular form and dose of activator, age of the thrombus, and route of administration. J Clin Invest 1983; 71: 368-376
• 10 Holvoet P, Lijnen HR, Collen D. A monoclonal antibody specific for Lys-plasminogen. Application to the study of the activation pathways of plasminogen in vivo. J Biol Chem 1985; 260: 12106-12111
• 11 Suenson E, Liitzen O, Thorsen S. Initial plasmin-degradation of fibrin as the basis of a positive feedback mechanism in fibrinolysis. Eur J Biochem 1984; 140: 513-522
• 12 Harpel PC, Chang T, Verderber E. Tissue plasminogen activator and urokinase mediate the binding of Glu-plasminogen to plasma fibrin I. Evidence for new binding sites in plasmin-degraded fibrin I. J Biol Chem 1985; 260: 4432-4440
• 13 Trail-Tang C, Kiuithof E KO, Atkinson J, Bachmann F. High-affinity binding sites for human Glu-plasminogen unveiled by limited plasmic degradation of human fibrin. Eur J Biochem 1986; 160: 599-604