APPEARANCE OF BASIC FIBROBLAST GROWTH-FACTOR RECEPTORS UPON DIFFERENTIATION OF RAT MAMMARY EPITHELIAL TO MYOEPITHELIAL-LIKE CELLS IN CULTURE

The binding of [125I]‐epidermal growth factor (EGF) and [125I]‐basic fibroblast growth factor (bFGF) to a number of single‐cell cloned rat mammary cell lines was measured using a saturation assay. Similar numbers of high‐affinity [125I]‐EGF binding sites (KD 1.3 nM) were found in epithelial and myoepithelial‐like cell lines. In contrast, high‐affinity (KD 35–276 pM) [125I]‐bFGF binding sites were present on fibroblastic and myoepithelial‐like cell lines but were not detectable on epithelial cell lines. A series of cell lines representing stages in the differentiation pathway of epithelial cells to an elongated myoepithelial‐like morphology showed a graded increase in the number of bFGF receptors. The sensitivity of a cell line to stimulation of DNA synthesis by bFGF correlated with the level of expression of bFGF receptors on the cellular surface. Complexes of cell surface receptors affinity‐cross‐linked to [125I]‐bFGF were analysed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE). In each case two distinct complexes having apparent molecular weights of 180 kDa and 160 kDa were observed. Copyright © 1990 Wiley‐Liss, Inc.