The insulin-like growth factors (IGFs) and IGF binding proteins in postnatal development of murine mammary glands.
The insulin-like growth factors are mitogens and survival factors for normal mammary epithelial cells in vitro. Data reviewed here demonstrate that mRNAs for IGF-I and IGF-II, the IGF type I receptor and the IGFBPs are expressed locally in mammary tissue during pubertal and pregnancy-induced growth and differentiation of murine mammary glands. IGF-I, IGF-II and the IGF-IR were expressed in terminal end buds (TEBs) in virgin glands during ductal growth. In addition, IGF-II and IGF-IR mRNAs were expressed in ductal and alveolar epithelium in glands throughout postnatal development. Consistent with these results, IGF-I promoted ductal growth and proliferation in mouse mammary glands in organ culture. In addition to endogenous expression of the IGFs and IGF-IR, the IGFBPs showed a varied pattern of expression in mammary tissue during postnatal development. For example, IGFBP-3 and -5 mRNAs were expressed in TEBs and ducts while IGFBP-2 and -4 mRNAs were expressed in stromal cells immediately surrounding the epithelium. These results support a role for the IGFs and IGFBPs as local mediators of postnatal mammary gland growth and differentiation.
Wood
T L
TL
Department of Neuroscience and Anatomy, Pennsylvania State University College of Medicine, Hershey 17033, USA. twood@psu.edu
Richert
M M
MM
Stull
M A
MA
Allar
M A
MA
D000818:Animals; D005260:Female; D018507:Gene Expression Regulation, Developmental; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D008321:Mammary Glands, Animal / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D051379:Mice; D011247:Pregnancy; D012741:Sexual Maturation
D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II