Plasminogen activator–induced dissolution of fibrin clots. (A) Fibrin clots containing plasminogen and varying amounts of myosin were prepared in microtiter plates and the activator-induced lysis was monitored as described in “Materials and methods.” The concentration of myosin in the clots was 0 (solid line), 0.2 μM (dotted line), or 2 μM (dashed and dotted line). The symbols indicate the mean of the t_1/2 lysis time and its SE determined from 5 replicate measurements. The inset shows the lysis time in relative units (the t_1/2 of fibrin without myosin is 1) determined under identical conditions for 0.3 μM tPA(•) and 0.15 μM urokinase (○) in quadruplicate samples. (B) Plasma clot formation and tPA-induced dissolution was monitored as described in “Materials and methods.” Representative curves are shown for plasma clots with no myosin (solid line), 0.5 μM myosin (dotted line), and 3 μM myosin (dashed and dotted line). • indicate the lysis time of the respective sample.