title: The direct in vitro effect of insulin-like growth factors (IGFs) on normal bovine mammary cell proliferation and production of IGF binding proteins.
abstract: Mammary epithelial cells isolated from pregnant, nonlactating heifers were grown in vitro using collagen substrates. Using these systems, the truncated form of insulin growth factor-1 (IGF-1) (des-3-IGF-1), IGF-1, and IGF-2 all stimulated a significant (0.5 to 1 fold) increase in cell proliferation (des-3-IGF-1 greater than IGF-1 greater than IGF-2). When grown in media containing serum plus IGF-1, normal bovine mammary cells also produced and secreted at least four species of IGF-binding protein (IGFBP) ranging from 21K to 48K (as demonstrated by ligand blot analysis). However, cells grown in serum free media secreted detectable quantities of only 2 major forms of IGFBP of 34K and 48K. Using immunoblot analysis, these proteins were identified as IGFBP-2 and IGFBP-3, respectively. Both proteins were inducible by the addition of IGF to the serum free media (relative potency; IGF-1 greater than des-3-IGF-1 greater than IGF-2). Using RIA analysis, bovine mammary cells cultured in the presence of IGF-1 produced 20-25 ng/ml IGFBP-2 compared to control cultures which secrete approximately 1.0 ng/ml. Cells exposed to des-3-IGF-1 produced 40-60% less IGFBP-2 whereas insulin and IGF-2 did not stimulate significant IGFBP-2 production. These data indicate that normal bovine mammary cells secret IGFBP-2 and IGFBP-3. This secretion is stimulated by IGF-1 and des-3-IGF-1 suggesting a mechanism for regulating local IGF activity.
authors.affiliation: Monsanto Agricultural Company, St. Louis, Missouri 63198.
authors.forename: M F
authors.initials: MF
authors.lastname: McGrath
authors.forename: R J
authors.initials: RJ
authors.lastname: Collier
authors.forename: D R
authors.initials: DR
authors.lastname: Clemmons
authors.forename: W H
authors.initials: WH
authors.lastname: Busby
authors.forename: C A
authors.initials: CA
authors.lastname: Sweeny
authors.forename: G G
authors.initials: GG
authors.lastname: Krivi
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000096:biosynthesis*; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D005260:Female; D018971:Insulin-Like Growth Factor Binding Protein 2; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D008321:Mammary Glands, Animal / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; D018971:Insulin-Like Growth Factor Binding Protein 2; D018969:Insulin-Like Growth Factor Binding Proteins; D010446:Peptide Fragments; C058957:insulin-like growth factor 1, des-(1-3)-; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II