bFGF neutralizing antibody inhibits HIF-1α protein accumulation at a late time. (A) HUVECs were seeded in GF^– medium and then cultured under normoxic or hypoxic conditions for 4, 8, 16 and 24 hours. HIF-1α protein accumulation was assessed by immunoblotting (B-C) HUVECs were seeded in GF^– medium and then cultured under normoxic or hypoxic conditions for 6 or 16 hours in the presence or absence of specific neutralizing antibodies for IGF-1, VEGF, bFGF, and PDGF-BB (100 ng/mL). HIF-1α protein accumulation was assessed by immunoblotting. (D) HUVECs were seeded in GF^– medium and then cultured for 16 hours under normoxic conditions in the presence or absence of bFGF (20 ng/mL) or under hypoxic conditions. HIF-1α protein accumulation was assessed by immunoblotting; β-actin is shown as loading control.