title: [125I]EGF binding ability is stable throughout the replicative life-span of WI-38 cells.
abstract: Using a serum-free medium supplemented with hormones and growth factors, which included epidermal growth factor (EGF), we investigated the binding and processing-degradation of [125I]EGF in WI-38 cells of various in vitro ages. The binding and processing-degradation systems of these cells remained essentially unchanged throughout their lifespan. The number of specific [125I]EGF binding sites per cell increased as the cultures senesced, though the number of specific binding sites per micron 2 (surface area) remained constant. The kinetics of ligand degradation as well as the qualitative and quantitative nature of the degradation products also remained essentially unchanged throughout the life-span. The only consistent alteration in any of the binding parameters measured was the slight decrease in the apparent Kd of the ligand-receptor complex, independent of temperature. Quantitation of EGF-stimulated DNA synthesis revealed a decrease in the percentage of cells incorporating [3H]thymidine ([3H]TdR) during a 30-h exposure from 45% in young cells to 0.25% in senescent cells, although [125I]EGF binding or processing-degradation did not differ significantly in young and old cells. Thus, EGF binding does not decrease in senescence.
mesh_terms: D002470:Cell Survival; D004705:Endocytosis; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors; D006801:Humans; D011956:Receptors, Cell Surface / Q000378:metabolism*
chemical_list: D011956:Receptors, Cell Surface; D004815:Epidermal Growth Factor; D066246:ErbB Receptors