Effect of TSP-1 and TSP-1 fragments on the release of FGF-2 from the ECM. Biotin-labeled FGF-2 (2-4 ng/well) was incubated onto the matrix for 3 hours and washed to remove unbound factor. The matrix was exposed to (A) different concentrations of TSP-1 (•) or 100 μg/mL heparin (used as a control; dotted line); (B) TSP-1 or its fragments (170 nM). The amount of mobilized FGF-2 present in the supernatant was analyzed by Western blot. Following densitometric analysis of the Western blot, released FGF-2 is expressed as the percentage of total FGF-2 bound to the matrix (mean ± SD). Data are from one experiment representative of at least 2 experiments.