ABSTRACT
Growth factors are polypeptide hormones that induce replicative DNA synthesis and cell division in their target cells. The molecular mechanisms of action and the in vivo functions of growth factors are not well understood. By far the most extensively studied growth factors are epidermal growth factor (EGF) and platelet-derived growth factor (PDGF). EGF is a single polypeptide chain (mol wt 6045), routinely isolated from the mouse submaxillary gland, that stimulates the proliferation of epithelial cells in vivo and of various other cell types in culture. 1 PDGF is a highly basic glycoprotein (30 to 33 kdaltons) that is released from platelets during blood clotting and at sites of blood vessel injury, where it may serve to promote wound healing by stimulating the proliferation of fibroblasts, glial cells, and smooth muscle cells. 2
