Fibronectin, not laminin, mediates heparin-dependent heparin-binding growth factor type I binding to substrata and stimulation of endothelial cell growth.

Fibronectin and heparin-binding growth factors (HBGF) are essential for growth of cultured endothelial cells. The stimulation of endothelial cell growth by HBGF type one (HBGF-1) in particular requires heparin or a similar glycosaminoglycan. The requirement for fibronectin and heparin for HBGF-1-stimulated endothelial cell growth may be related. HBGF-1 absorbed to the natural subcellular matrix of endothelial cells supports cell growth. [125I]HBGF-1 specifically associates with a sequentially reconstituted matrix of collagen-fibronectin-heparin, and HBGF-1 absorbed to the reconstituted matrix supports growth of the endothelial cells. A reconstituted matrix of collagen-laminin-heparin neither supported binding of [125I]HBGF-1 nor HBGF-1-stimulated endothelial cell growth. Association kinetics of [125I]HBGF-1 to heparinlike sites and membrane receptor sites on endothelial cell monolayers suggest that fibronectin-heparinlike binding sites in the subcellular matrix may be an obligatory reservoir of active HBGF-1 that binds to specific cell membrane receptors.