Plasminogen activator inhibitor-1 (PAI-1), which is secreted from vascular endothelial cells, plays an important role in regulating fibrinolysis. We measured the plasma concentrations of tissue-type plasminogen activator (t-PA), PAI-1 and t-PA PAI complex before and serially after thrombolytic therapy for acute myocardial infarction to clarify the relationship between thrombolytic therapy and PAI-1. Plasma concentrations of t-PA, PAI-1 and t-PA PAI complex before thrombolytic therapy were 11.6 ± 5.5, 27.0 ± 13.0 and 7.3 ± 5.4 ng/ml, respectively. t-PA and t-PA PAI complex increased to 25.0 ± 5.3 and 14.3 ± 6.5 ng/ml immediately after drug administration; however, the level of PAI-1 decreased slightly immediately after thrombolytic therapy. The PAI-1 level increased again several hours after therapy, especially in patients showing apparently successful reperfusion. All values returned to normal 4-7 days after thrombolytic therapy. Not only augmented antifibrinolytic activity suggested by increased PAI-1 but also augmented fibrinolytic activity suggested by increased t-PA was observed in patients with acute myocardial infarction. These abnormal findings persisted several days after coronary thrombolytic therapy.
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