Effect of suPAR on scuPA-mediated clot lysis: release of radioactivity. (A) Lysis of fibrin versus plasma clots. Left side: clots prepared from purified bovine fibrinogen. scuPA (10 pmol in 10 μL PBS; open bar) or equimolar concentrations of scuPA/suPAR complex (solid bar) was incubated with clots prepared from¹²⁵I-labeled human fibrinogen for 2 hours at 37°C, and the radioactivity released into the supernatant was measured. The data are expressed relative to the condition that produced maximal fibrinolysis. In this and in each panel below, the mean ± standard error of the mean (SEM) of three experiments is shown. Right side: plasma clots. Plasma clots, trace labeled with¹²⁵I-fibrinogen, were prepared as described in Fig 1B. scuPA (open bar) or scuPA/suPAR (solid bar) was added for 2 hours at 37°C, and the radioactivity released into the supernatant was measured. (B) Lysis of plasma clots. Left side: effect of ATF.¹²⁵I-labeled plasma clots were incubated with scuPA/suPAR (10 pmol in 10 μL PBS) alone or in the presence of 500 pmol ATF for 2 hours at 37°C, and the radioactivity released into the supernatant was measured. Right side: Effect of scuPA-glu¹⁵⁸. scuPA-glu¹⁵⁸ (10 pmol in 10 μL PBS; designated *scuPA) was added to ¹²⁵I-labeled plasma clots in the absence or presence of equimolar concentrations of suPAR for 2 hours at 37°C, and the radioactivity released into the supernatant was measured.