We report here that platelet-derived growth factor (PDGF)1-4 and pituitary-derived fibroblast growth factor (FGF)5 bind rapidly and tenaciously to tissue culture plates either coated with collagen (a major component of the extracellular matrix) or uncoated. Surface-bound PDGF resists extraction with non-ionic detergents, organic solvents and chaotropic solvents; moreover it is biologically active in situ. Our finding that immobilized PDGF is nonetheless mitogenic lends support to other observations which indicate that PDGF functions outside the cell via production of a stable intracellular second signal6. In a broader context, the observations suggest that one role of the extracellular matrix in vivo is to sequester biologically active molecules like PDGF to provide a localized and persistent stimulation.
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