FGF-2 is released from the matrix by TSP-1 as an FGF-2/TSP-1 complex. ECM was incubated with FGF-2 and then exposed to TSP-1. The samples, containing FGF-2 released from the matrix, were then analyzed as follows. (A) Gel filtration chromatography. FGF-2 released from the ECM by TSP-1 (continuous line) or by 2 M NaCl (dashed line) were loaded on an S200 column and the eluted fractions were analyzed by dot-blot analysis using anti-FGF-2 antiserum. V_o = void volume, elution volume for TSP-1; FGF-2, elution of control, free FGF-2. (B) Chemical cross-linking. Samples containing biotin-labeled FGF-2 released from the matrix by TSP-1 or heparin, or that was spontaneously released (control) were treated with the cross-linking agent DSS and analyzed by Western blot. Arrows indicate the high-molecular-weight bands consistent with a TSP-1/FGF-2 complex; arrowhead, free FGF-2; and asterisk, the edge of the separating gel. Molecular weight markers (in kDa) are on the left.