Effect of uPA concentration on plasmin generation rates in the presence of Nalm6 cells. Plasmin generation rates were measured in the presence of 1.1 × 10⁷ cells/mL, 100 nmol/L glu-plasminogen, and increasing concentrations of HMW uPA (•), scuPA (⧫), and LMW uPA (▴). Open symbols show the activation rates under the same conditions, but in the absence of cells. Activation rates are shown as mean ± SE, n = 2.