Plasminogen Activator, Urokinase Receptor (uPAR) is the receptor for urokinase plasminogen activator and, given its role in localizing and promoting plasmin formation, likely influences many normal and pathological processes related to cell-surface plasminogen activation and localized degradation of the extracellular matrix. The urokinase receptor (uPAR) was identified as the membrane receptor of the serine protease urokinase (uPA), thereby implicated in the plasminogen activation cascade and regulation of pericellular proteolysis, thus a binding ELISA assay was conducted to detect the interaction of recombinant rat uPAR and recombinant human uPA. Briefly, biotin-linked uPAR were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 ul were then transferred to uPA-coated microtiter wells and incubated for 1h at 37 ℃. Wells were washed with PBST 3 times and incubation with Streptavidin-HRP for 30min, then wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37 ℃. Finally, add 50 µl stop solution to the wells and read at 450 nm immediately. The binding activity of uPAR and uPA was shown in Figure 1, the EC50 for this effect is 0.223 ug/mL.