Effect of plasminogen on the plasminogen activator activity of suPAR/scuPA in presence of plasma-derived clots. Plasminogen-depleted plasma containing ¹²⁵I-fibrinogen was supplemented with increasing concentrations of plasminogen. Clots were formed by adding thrombin. scuPA/suPAR (25 nM) was added for 2 hours at 37°C and the release of radioactivity into the supernatant was measured.