Binding of ¹²⁵I–PF-4 to endothelial cells and cells deficient of heparan sulfates and expressing FGFR-1. LEII cells or CHOm–FGFR-1 cells (500,000 cells/dish) were incubated with¹²⁵I–PF-4 in the presence or absence of unlabeled ligand and binding to high-affinity (HA, cell surface–bound¹²⁵I–PF-4 extracted with 2 mol/L NaCl buffer at pH 4) or low-affinity sites (LA, cell surface–bound ¹²⁵I–PF-4 extracted with 2 mol/L NaCl buffer at pH 7.4) were analyzed as indicated in Materials and Methods. The binding of the figure depicts representative experiments done in duplicates (data points as mean + SD).