Fig. 5. Characterisation of the VEGFR-1/5ß1 integrin interaction. (A) Dose-dependent VEGFR-1 binding to purified 5ß1-coated wells. Different concentrations (10^-1-10⁴ ng/ml) of VEGFR-1/Fc were added to 5ß1 coated wells (1 µg/ml) and bound molecules were detected using an anti-human IgG (Fc specific)-alkaline phosphatase conjugated antibody. Results represent the mean absorbance value of medium from triplicate wells ± s.e.m. (B) VEGFR-1/Fc and VEGFR-2/Fc (20 µg/ml) were added to 5ß1-coated wells. In competition experiments, EDTA (1 mM) or a blocking anti-5ß1 antibody (10 µg/ml) was added during the assay. Absorbance resulting from non-specific cell adhesion was measured on BSA-coated wells. Histograms represent the mean absorbance value of medium from triplicate wells ± s.e.m. (C) Effect of RGD peptides or VEGFR-1 growth factor ligands on cell attachment. Cells were pretreated with 0.4 mM of RGD or RGE peptides, before plating on fibronectin (FN) or VEGFR-1/Fc (5 µg/ml), or the adhesion assays were performed in the presence of 20 µg/ml VEGF and placenta growth factor (PlGF). Results are expressed as the percentage of adherent cells compared to untreated controls.