Effect of TSP-1 and TSP-1 fragments on FGF-2 binding to the ECM. (A) Biotin-labeled FGF-2 (1-2 ng/well) was added to the matrix laid by BAEC (•), HUVECs (▪), or to Matrigel (▴) in the presence of different concentrations of soluble TSP-1 (continuous lines). To test the effect of matrix-bound TSP-1 (dotted line) the matrix was pretreated with 220 nM TSP-1 and washed before the addition of labeled FGF-2. (B) Biotin-labeled FGF-2 was incubated on the ECM with different concentrations of TSP-1 (⋄) or its 140-kDa fragment (▪), its 25-kDa fragment (▵), or the 2 fragments together (•). After a 3-hour incubation, the matrix was washed to remove unbound FGF-2 and the amount of matrix-bound FGF-2 was evaluated using the ExtrAvidin-peroxidase/OPD system. Data (mean ± SD of triplicates) are expressed as the percentage of control binding (bound FGF-2 in the absence of inhibitor). Results are from one experiment representative of at least 3 experiments.