Recombinant lys-plasminogen, but not glu-plasminogen, improves recombinant tissue-type plasminogen activator-induced coronary thrombolysis in dogs.

OBJECTIVES

This study examined the modification of recombinant tissue-type plasminogen activator (rt-PA)-induced thrombolysis by recombinant lys-plasminogen.

BACKGROUND

Recombinant tissue-type plasminogen activator restores flow in the thrombosed coronary artery, but the artery often reoccludes. The rt-PA-induced thrombolysis is a result of activation of plasminogen bound to fibrin in the thrombus and results in generation of the fibrinolytic enzyme plasmin. Small amounts of lys-plasminogen are formed when rt-PA is used. Lys-plasminogen binds to fibrin with a 10-fold greater affinity than the predominant native glu-plasminogen, leading to a loose fibrin structure.

METHODS

Dogs with electrically induced occlusive intracoronary thrombus were treated with saline solution (n = 9), glu-plasminogen (2 mg/kg body weight, n = 5) or lys-plasminogen (2 mg/kg, n = 5), followed by infusion of rt-PA (1 mg/kg over 20 min) 10 min later.

RESULTS

Reperfusion rates were similar in all groups of dogs, but the time to reflow was lowest in dogs given lys-plasminogen compared with those given saline solution or glu-plasminogen before rt-PA (mean [+/- SE] 14 +/- 2 vs. 22 +/- 2 and 23 +/- 3 min, respectively, p < 0.05). None of the reperfused coronary arteries reoccluded in the lys-plasminogen plus rt-PA group, whereas 75% reoccluded in dogs given saline solution plus rt-PA, and 50% reoccluded in those given glu-plasminogen plus rt-PA. Accordingly, duration of reflow was greater in the lys-plasminogen plus rt-PA group (> 120 vs. 39 +/- 7 and 82 +/- 21 min, respectively, p < 0.05). Plasminogen activator inhibitor-1 activity decreased during rt-PA infusion and thereafter increased in all dogs, but less so in dogs given lys-plasminogen (p < 0.05 vs. those given saline solution before rt-PA).

CONCLUSIONS

Treatment with recombinant lys-plasminogen before rt-PA reduces time to reflow and sustains reflow after thrombolysis, whereas glu-plasminogen has no such effect.