(A) BMDMs were serum-starved for 30 min and then treated with 12 nM enzymatically-active tPA (EA-tPA), plasminogen (Plg) at the indicated concentrations, and S-2251 (0.2 mM). The plots marked “EA-tPA” and “S-2251” show substrate hydrolysis in cultures treated with EA-tPA and S-2251 in the absence of Plg and with S-2251 alone, respectively. (B) Serum-starved BMDMs were incubated with Plg at the indicated concentrations and S-2251. As a control, S-2251 was added to cultures alone. (C) BMDMs were incubated with EI-tPA, Plg (200 nM or 500 nM), and S-2251. The graphs marked “EI-tPA” and “S-2251” show substrate hydrolysis in cultures treated with EI-tPA and S-2251 in the absence of Plg or S-2251 alone, respectively. The absorbance at 405 nm was determined every 10 min for 70 min. Overlapping data points preclude distinguishing individual points when substrate hydrolysis did not occur (mean ± SEM, n = 6).