Inhibition of binding of basic fibroblast growth factor to low and high affinity receptors by carrageenans

The effect of carrageenans, a family of polysulphated polysaccharides, on the binding of basic fibroblast growth factor (bFGF) to low affinity (heparin-like) receptors and high affinity receptors on baby hamster kidney cells was investigated. kappa-, iota-, and lambda-carrageenans all inhibited binding of bFGF to both types of receptors with iota-carrageenan being the most potent inhibitor (IC50 values of approx. 0.7 and 4 micrograms/mL for inhibition of binding to low and high affinity receptors respectively). Heparin reduced the inhibition of bFGF binding to high affinity receptors caused by iota-carrageenan. Heparin and iota-carrageenan were comparable in their activities at displacing pre-bound bFGF from both low affinity receptors and high affinity receptors. These results indicate that iota-carrageenan binds to the heparin-binding domain on bFGF and that this may be sufficient to reduce the ability of bFGF to bind to high affinity receptors.