tPA-catalyzed plasminogen activation on VSMCs. VSMCs in suspension were preincubated with tPA (10 nmol/L) and washed, and plasmin generation was determined after the addition of either Glu-plasminogen (200 nmol/L) or Lys-plasminogen (20 nmol/L) and H-D-Val-Leu-Lys-AMC (0.2 mmol/L). In (A), data are shown for Glu-plasminogen activation assayed in the absence (▪) and presence (•) of 6AHA (1 mmol/L) as an antagonist of plasminogen binding. Also shown (○) are the data in the presence of 6AHA corrected for its direct stimulatory effect on plasminogen activation (see the Materials and Methods). (B) shows data for Lys-plasminogen activation in the absence (□) and presence (○) of 6AHA.