Effect of heparin on the binding affinity of acidic FGF for the cloned human FGF receptors, flg and bek

Heparin potentiates the mitogenic activity of acidic fibroblast growth factor (aFGF) by 20–100 fold but mechanisms detailing this potentiation have not yet been fully elucidated. We report that heparin increases the binding affinity of aFGF for the two cloned and overexpressed human FGF receptors, flg and bek, by 2–3 fold. This increase in binding affinity, together with previous data demonstrating a 3–5 fold increase in the stability of aFGF, are likely to account for a significant portion of heparin's potentiation of aFGF activity observed in biological assay systems.