title: Receptor binding and growth-promoting activity of insulin-like growth factor-I in a bovine mammary epithelial cell line (MAC-T3).
abstract: Insulin-like growth factor-I (IGF-I) has been known to be mitogenic to a variety of cell types, although a growth-regulatory role for IGF-I on bovine mammary epithelial cells has not been fully investigated. In the present study, we examined the receptor binding of IGF-I and its effect on growth in a bovine mammary epithelial cell line (MAC-T3). Specific receptors for IGF-I were detected on cultured bovine mammary epithelial cells. Competitive binding revealed that half-maximal inhibition of 125I-labelled IGF-I binding by IGF-I was approximately 3 micrograms/l. Dissociation rate constant of the IGF-I receptor was 3.10 +/- 0.06 nmol/l (S.E.M.) with a receptor site concentration of 366 +/- 8 fmol/mg protein for the average of three experiments. IGF-I exerted a positive mitogenic effect on MAC-T3 cells according to both direct DNA assay and thymidine incorporation assay. Moreover, the mitogenic effect of IGF-I on MAC-T3 cells was enhanced by the addition of fetal calf serum in the culture media. The present results suggest that the bovine mammary epithelial cell line (MAC-T3) provides a useful model system with which to study the biological actions of insulin-like growth factors on the bovine mammary secretory tissue in vitro.
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Ontario, Canada.
authors.forename: X
authors.initials: X
authors.lastname: Zhao
authors.forename: B W
authors.initials: BW
authors.lastname: McBride
authors.forename: I
authors.initials: I
authors.lastname: Politis
authors.forename: H T
authors.initials: HT
authors.lastname: Huynh
authors.forename: R M
authors.initials: RM
authors.lastname: Akers
authors.forename: J H
authors.initials: JH
authors.lastname: Burton
authors.forename: J D
authors.initials: JD
authors.lastname: Turner
mesh_terms: D000818:Animals; D002417:Cattle; D002460:Cell Line; D004848:Epithelium / Q000254:growth & development / Q000378:metabolism; D005260:Female; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D008938:Mitosis / Q000187:drug effects*; D011485:Protein Binding
chemical_list: D007334:Insulin-Like Growth Factor I