title: Modulation of EGF-receptors by phorbol ester in small intestinal crypt cells.
abstract: We have previously shown that EGF promotes growth and proliferation of enterocytes isolated from the crypts of the rat small intestine (IEC-6). In the present studies we have measured the affinity of EGF for its receptor, and estimated the number of surface EGF receptors on IEC-6 cells. Scatchard analysis indicates IEC-6 cells display 45,000 EGF receptors per cell with a dissociation constant of 41 pM. Treatment with phorbol-12-myristate-13-acetate (PMA) results in a dose-dependent inhibition of cell growth which is paralleled by reduced binding of 125I-EGF. Incubation of IEC-6 cells with 10 nM PMA results in a 70 percent decrease in the number of EGF receptors without a significant change of receptor affinity (kd 68 pM vs 41 pM). PMA treatment is also associated with a significant increase of protein kinase-C activity in IEC-6 cells. The reciprocal relationship between protein kinase-C activation and EGF receptors suggests in this cell line of crypt enterocytes, protein kinase-C may inhibit cellular proliferation by modulating EGF receptors.
authors.affiliation: Department of Pediatrics, University of South Alabama College of Medicine, Mobile 36617.
authors.forename: B S
authors.initials: BS
authors.lastname: Baliga
authors.forename: S M
authors.initials: SM
authors.lastname: Borowitz
authors.forename: J A
authors.initials: JA
authors.lastname: Barnard
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D007700:Kinetics; D011493:Protein Kinase C / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate