VEGF and VEGFf binding interactions. A: VEGF/VEGFf binding to ECM from pulmonary fibroblasts. 125I -VEGF (open) or 125I -VEGFf (filled) was incubated for 3 hours at 4°C and bound growth factor was determined. Significant differences between VEGF and VEGFf binding was found. B: VEGF/VEGFf binding to fibronectin ± heparin. 125I-VEGF (circles) or 125I-VEGFf (diamonds) bound to fibronectin alone (open) or with heparin (filled). C: VEGF/VEGFf binding to NP-1. 125I -VEGF or 125I -VEGFf at 0.25 (filled) and 1 (open) nM were incubated with Fc-NP-1 for 2 h and complexes determined. Significant differences were found between VEGF bound in the presence of 0.5 nM NP-1 compared to no NP-1, and with 0.25 nM VEGF in the presence of 0.1 nM NP-1 compared to no NP-1. No significant differences were noted for VEGFf ± NP-1. D: VEGF/VEGFf binding to VEGFR1 and NP-1. 0.25 nM 125I -VEGF or 125I -VEGFf was incubated alone (white) or with Fc-VEGFR1 (0.1 nM, dark grey), Fc-NP-1 (0.5 nM, light grey), or both VEGFR1 and NP-1 (black) for 2 h; complexes were pulled down and 125I-VEGF/VEGFf counted. Significant differences were observed with all VEGF bound groups, and between VEGFf bound in the presence versus the absence of VEGFR1. No significant difference was noted between VEGFf bound to VEGFR1 ± NP-1. Data are the mean of quadruplicate (A,C) triplicate (D) or duplicate (B) determinations ± SD. ANOVA followed by multi-comparison t-tests was performed for statistical analysis.