BINDING OF BASIC FIBROBLAST GROWTH-FACTOR TO FIBRINOGEN AND FIBRIN

Fibrin is formed at sites of tissue injury and provides the temporary matrix needed to support the initial endothelial cell responses needed for vessel repair. Basic fibroblast growth factor (bFGF) also acts at sites of injury and stimulates similar vascular cell responses, We ha ve, therefore, investigated whether there are specific interactions be tween bFGF and fibrinogen and fibrin that could play a role in coordin ating these actions, Binding studies were performed using bFGF immobil ized on Sepharose beads and soluble I-125-labeled fibrinogen and also using Sepharose-immobilized fibrinogen and soluble I-125-bFGF. Both sy stems demonstrated specific and saturable binding, Scatchard analysis indicated two classes of binding sites for each with K-d values of 1.3 and 260 nM using immobilized bFGF; and K-d values of 0.9 and 70 nM us ing immobilized fibrinogen, After conversion of Sepharose-immobilized fibrinogen to fibrin by treatment with thrombin, bFGF also demonstrate d specific and saturable binding with two classes of binding sites hav ing K-d values of 0.13 and 83 nM, Fibrin binding was also investigated by clotting a solution of bFGF and fibrinogen, and two classes of bin ding sites were demonstrated using this system with K-d values of 0.8 and 261 nM. The maximum molar binding ratios of bFGF to fibrinogen wer e between 2.0 and 4.0 with the four binding systems, We conclude that bFGF binds specifically and saturably to fibrinogen and fibrin with hi gh affinity, and this may have implications regarding the localization of its effect at sites of tissue injury.