Susceptibility of fibrinolysis to PAI-1.¹²⁵I-labeled fibrin clots in PBS (−) or PBS supplemented with 50 nmol/L PAI-1 (+) were incubated with 25 nmol/L scuPA/suPAR, tcuPA, or tcuPA/suPAR for 200 minutes at 37°C, and the radioactivity released into the supernatant was measured. The mean ± SEM of three experiments is shown.