Fig. 3. 5ß1 integrin mediates EC attachment to VEGFR-1. (A) Effect of divalent cations and trypsin treatment on EC adhesion to VEGFR-1. Cells were plated on fibronectin (FN), BSA or VEGFR-1/Fc in the presence of EGTA, EDTA, Ca²⁺, Mg²⁺, Mn²⁺ or trypsin, and after checking cell viability by trypan-blue dye exclusion in control wells, the relative number of attached cells was estimated as described in Fig. 2. Histograms represent the mean absorbance value of medium from triplicate wells ± s.e.m. (B) Cells were incubated with mAbs against ß1, 5, 6 (unrelated Ab), 5ß1 and vß3 15 minutes before plating on VEGFR-1/Fc, fibronectin (FN) or vitronectin (VN). Histograms represent the percentage of inhibition, calculated relative to the adhesion of cells on the same substrates in the absence of blocking antibodies, ± s.e.m. The experiments in A and B were repeated at least three times.