Role of α2Plasmin Inhibitor in Fibrinolytic Therapy by Urokinase and the Optimal Urokinase Dosage
A novel plasmin inhibitor, namely α2plasmin inhibitor (α2PI), was found to be more efficient than other plasmin inhibitors but its clinical role in fibrinolytic therapy by urokinase (UK) was not examined. We injected UK into 9 patients with thrombotic diseases at several different doses (2-180×l04 IU/day) in order to estimate the optimal dosage inducing fibrinolysis, ahd to evaluate the role of α2PI in fibrinolysis during UK administration. The correlation coefficients(CE) between UK/day and α2PI, plasminogen (PIg), ulantitrypsin (UIAT) and α2macroglobulin(α2MC) were-0.75, -0.54, 0.39 and -0.37, respectively. Above50×104 of UK/day, the α2PI level fell below 60%, and above 150×10 4 IU of UK/day it fell below 30%. The CE between lysis area on fibrin plate (FPL) and α2PI, α2AT, α2MC, UK/day and PIg were -0.69, 0.51, -0.31, 0.30 and -0.26, respectively. When the level of α2PI fell below 60%, EPL was observed in 13 of 20 samples (65%) , whereas above 60% of α2PI it was observed in only 4 of 35 samples (11%). The above results suggest that α2PI is most important in regUlating fibrinolysis during UK administration and about 50xl0 4IU/day of UK should be infused in order to lower the level of α2PI to below 60%, so inducing prominent fibrinolysis.