¹²⁵I-labeled tPA binding to VSMCs. The binding of ¹²⁵I-labeled tPA to VSMCs is shown in the absence (▪) and presence (•) of 1 μmol/L cold tPA, together with specific binding calculated from these data (□). The inset shows a comparison of the competition of total ¹²⁵I-labeled tPA binding (0.5 nmol/L) by both cold tPA and by anti–PAI-1 MoAb (7F4) and polyclonal antibody at a concentration of 50 μg/mL. All data shown are the mean ± SD of triplicate determinations.