title: Epidermal growth factor-induced down-regulation of receptor does not occur in HeLa cells grown in defined medium.
abstract: 125I-Labeled epidermal growth factor (EGF) binds to HeLa cells in culture under completely defined conditions in a specific and saturable manner. When the cultures are maintained in serum, all the reported phenomena of down-regulation occur. In contrast, in cultures maintained in serum-free hormone-supplemented medium, binding is maximal after 50 min and remains constant for at least 18 hr. EGF retains its mitogenic activity in this defined system; as little as 4 pM EGF elicits a 2-fold increase in cell number in 5 days. EGF appears to be in reversible equilibrium with a constant number of surface receptors, and gel filtration analysis indicates a decrease in the rate of degradation and release of bound 125I-labeled EGF. These results indicate that EGF can retain its mitogenic activity in the absence of concomitant down-regulation.
mesh_terms: D002455:Cell Division / Q000187:drug effects; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D006367:HeLa Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D010455:Peptides / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000187:drug effects* / Q000378:metabolism
chemical_list: D003470:Culture Media; D010455:Peptides; D011956:Receptors, Cell Surface; D004815:Epidermal Growth Factor