Synergism in the induction of Ang2 by VEGF and bFGF. (A) Dose-response curve for bFGF induction of Ang2. HUVECs were treated with constant VEGF (50 ng/mL) and increasing bFGF concentrations (0-250 ng/mL) for 20 hours. Levels of Ang2 were determined by Western blotting (α-tubulin levels are shown to indicate equal loading; n = 3). The intensity of the Ang2 bands was determined by autoradiography and densitometry as described in “Methods.” (B) Mean Ang2 levels were expressed as the percentage of control (VEGF, 50 ng/mL; bFGF, 0 ng/mL). The EC₅₀ value for the bFGF was calculated by nonlinear regression. (C) Synergism between VEGF and bFGF (VF) in the induction of Ang2 was established at optimal conditions (VEGF, 50 ng/mL; bFGF, 20 ng/mL) by Western blotting. “+” signifies Ang2-positive control.