Fig. 2: activation of plasminogen in the presence of Trypanosoma cruzi. 10 nM t-PA was added to a mixture, in a final volume of 100 µl, containing 200 nM plasminogen, 0.6 nM S2251 and different concentrations of epimastigotes (A) and metacyclic trypomastigotes (B). The absorbance at 405 nm, at different times, was determined. Insets, effect of cell density on t-PA-catalyzed plasminogen activation.