Regulation of insulin-like growth factor binding protein secretion by a murine mammary epithelial cell line.
The regulation of insulin-like growth factor binding protein (IGFBP) secretion by mammogenic and lactogenic hormones was investigated in a mouse mammary epithelial cell line (COMMA-D/MME). Cells were grown to confluency on plastic culture plates in serum-containing medium. The confluent cells were exposed to the hormonal treatments in serum-free medium for 6 days. Conditioned medium was collected on Days 5 and 6 and analyzed for IGFBPs by 125I-labeled insulin-like growth factor (IGF)-II ligand blotting and quantified by densitometry. IGFBP data were expressed as absorbance units x millimeters (AUxmm) that were corrected for DNA per well. In basal serum-free media, the COMMA-D/MME cells secreted predominantly IGFBP-3, but also some IGFBP-2. The mammogenic growth factors, IGF-I (13.3 nM) and epidermal growth factor (EGF; 1.7 nM), both stimulated DNA synthesis (P < 0.05); however, their effects on IGFBP-3 secretion differed. IGF-I stimulated IGFBP-3 secretion whereas EGF was inhibitory. In addition, EGF inhibited IGFBP-2 secretion and IGF-I tended to increase it. No interaction was observed between IGF-I and EGF for any of the parameters measured. Three lactogenic hormones (insulin, 154 nM; prolactin, 4.3 nM; and cortisol, 1.4 microM) in all combinations were tested to determine their effects on IGFBP secretion. Insulin stimulated IGFBP-3 secretion and DNA synthesis, but had no effect on IGFBP-2 secretion. Cortisol inhibited IGFBP-3 secretion and DNA synthesis, but increased IGFBP-2 secretion. Prolactin had no effect on any of the parameters examined. In summary, the COMMA-D/MME cells secrete IGFBP-2 and IGFBP-3 in serum-free media. Although the secretion of IGFBP-2 and IGFBP-3 in serum-free media. Although the secretion of IGFBP-2 and IGFBP-3 was regulated by several of the hormones and growth factors tested, no clear distinction was observed between the mammogenic and lactogenic treatments.
Skaar
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Department of Dairy and Animal Science, Pennsylvania State University, University Park 16802.
Baumrucker
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D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004847:Epithelial Cells; D006133:Growth Substances / Q000494:pharmacology; D006854:Hydrocortisone / Q000008:administration & dosage; D066298:In Vitro Techniques; D007328:Insulin / Q000008:administration & dosage; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D011388:Prolactin / Q000008:administration & dosage
D002352:Carrier Proteins; D006133:Growth Substances; D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D006854:Hydrocortisone