Effect of TSP-1 on the interaction of VEGF and HGF/SF with the subendothelial matrix. (A) Biotin-labeled FGF-2, VEGF, or HGF/SF was incubated on the ECM alone (control; □) or in the presence of 220 nM TSP-1 (▨) or 100 μg/mL heparin (▪). The amount of matrix-bound angiogenic factors, measured using the ExtrAvidin-peroxidase/OPD system is expressed as the percentage of control binding (mean ± SD of triplicate values). (B) After preincubation with FGF-2, VEGF, or HGF/SF, the ECM was treated with buffer (control), 220 nM TSP-1, or 100 μg/mL heparin. The samples released from the matrix were analyzed by Western blot. Results are from one experiment representative of at least 2 experiments.