Of the zymogen plasminogen) or when PAI-1 competes with uPAR for the VN somatomedin B domain (69). The ability of PAI-1 to competitively inhibit uPAR's binding to the extracellular matrix VN, thereby regulating VN-uPAR and VN-integrin-uPAR interactions, plays a key role in uPARdependent cell adhesion and migration (70, 71). Vitronectin expression in the tubulointerstitium is known to be up-regulat