(A through C) Effect of PF-4 on ¹²⁵I–FGF-2 binding to endothelial cells and cross-linking. LEII cells (500,000 cells/dish) were incubated at 4°C with 10 ng/mL¹²⁵I–FGF-2 and increasing concentrations of PF-4 in the absence or presence of 1 μg/mL unlabeled FGF-2.¹²⁵I–FGF-2 bound to high-affinity (A) or low-affinity binding sites (B) was determined as indicated in Materials and Methods. Nonspecific binding is indicated in black bars. Specific binding (ng/10⁶ cells) is shown as inset. (C) Cross-linking of ¹²⁵I–FGF-2 to receptors in the presence or absence of 10 μg/mL PF-4 or unlabeled ligand. (A and B) Representative experiment done in duplicates (data points as mean; SD values: [A] 0 < SD < 0.8; [A, inset] 0 < SD < 0.03; [B] 0.13 < SD < 0.8).