Fig. 2. VEGFR-1 supports EC attachment. (A) Dose-dependent cell attachment on wells coated with the indicated concentrations of VEGFR-1/Fc or fibronectin (FN). The relative number of attached cells was assessed by staining with crystal violet and determining the A₅₄₀ 1 hour after plating. Absorbance resulting from non-specific cell adhesion was measured on BSA-coated wells. (B,C) VEGFR-1-specific promotion of EC adhesion. (B) EC were plated on 10 µg/ml VEGFR-1/Fc-, VEGFR-2/Fc-, PDGFRß/Fc-, IgG-, or BSA-coated wells and cell adhesion was measured as described for A. (C) EC were plated on 10 µg/ml FN-, VEGFR-1/Fc-, or BSA-coated wells. Before cell seeding, wells were incubated for 30 minutes with undiluted preimmune serum or anti-VEGFR-1 rabbit serum. Alternatively, cells were treated with 20 µg/ml of VEGFR-1/Fc for 15 minutes before plating. Histograms represent the mean absorbance value of medium from triplicate wells ± s.e.m. The experiments were repeated at least five times.