Binding, internalization, and degradation of epidermal growth factor by balb 3T3 and BP3T3 cells: relationship to cell density and the stimulation of cell proliferation.
Epidermal growth factor (EGF) stimulates the growth of both benzo[a]pyrene-transformed Balb 3T3 cells (BP3T3) and untransformed Balb 3T3 cells. We describe here the binding, internalization, and degradation of [125I]-EGF by BP3T3 cells and 3T3 cells. Binding of [125I]-EGF reaches a maximum after 45 to 90 minutes incubation at 37 degrees C. In both BP3T3 and 3T3 cells the extent of EGF binding required to stimulate DNA synthesis is density dependent; sparse cultures require a 15-30% occupancy to elicit a maximal response whereas dense cultures require a 70-85% occupancy. At physiological concentrations the total binding of [125I]-EGF to 3T3 cells is higher than to BP3T3 cells, and this difference increases at higher cell densities. The rate of degradation of [125I]-EGF is directly proportional to the total [125I]-EGF binding in each cell type. This supports the hypothesis that one cause of the diminished serum requirement of BP3T3 cells is a reduced rate of utilization of serum growth factors.
D000818:Animals; D001580:Benzopyrenes / Q000494:pharmacology; D002452:Cell Count; D002455:Cell Division; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000378:metabolism; D002999:Clone Cells / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism*; D007668:Kidney; D051379:Mice; D008807:Mice, Inbred BALB C; D010455:Peptides / Q000378:metabolism*
D001580:Benzopyrenes; D010455:Peptides; D004815:Epidermal Growth Factor