Thromb Haemostasis
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A potential synergic effect of tissue-type plasminogen activator (t-PA), single-chain urokinase-type plasminogen activator (scu-PA) or urokinase on clot lysis was investigated in a whole human plasma system in vitro. The system consisted of a human plasma clot labeled with 125I-fibrinogen, immersed in citrated whole human plasma, to which the thrombolytic agents were added. Clot lysis was quantitated by measurement of released 125I, and activation of the fibrinolytic system in the surrounding plasma by measurements of fibrinogen and alpha 2-antiplasmin. t-PA, scu-PA and urokinase induced a dose-dependent and time-dependent clot lysis; 50 percent lysis after 2 h was obtained with 5 nM t-PA, 20 nM scu-PA and 12 nM urokinase. ⋯ The shape of the dose-response curves was different; t-PA and urokinase showed a log linear dose-response whereas that of scu-PA was sigmoidal. Combinations of t-PA and scu-PA, of t-PA and urokinase or of scu-PA and urokinase at thrombolytic doses of each showed no synergism for thrombolysis. Fifty percent clot lysis in 2 h was obtained at total concentrations of the combined agents of 5 to 15 nM with molar ratios ranging from 1:4 to 4:1.(ABSTRACT TRUNCATED AT 250 WORDS)