Estrogen Regulation of the Pituitary Insulin - Like Growth Factor System
Insulin-like growth factor I (IGF-I) and the closely related IGF-II are homologous to proinsulin and share many of insulin’s effects on cell metabolism. In addition they stimulate cellular differentiation and proliferation1. Circulating IGF-I originating mainly from the liver, has classical endocrine actions2, however, local IGF-I production in many other tissues suggests an autocrine/paracrine role as we113. Most biological actions of the IGFs are mediated through the IGF-I receptor (IGFR-I) which has intrinsic tyrosine kinase activity4,5 Specific, high-affinity, insulin-like growth factor binding proteins (IGFBPs), present in the plasma and extracellular space, also bind the IGFs, modulating their interaction with the IGF-I receptor and perhaps targeting IGFs to specific loci6. To date, six different IGFBPs have been characterized7, among which IGFBP2 is particularly abundant in the pituitary8.
KeywordsCholesterol Cellulose Ischemia Estrogen Tyrosine
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- 1.M.M. Rechler and S.P. Nissley, Insulin-like Growth Factors, in: “Peptide Growth Factors and Their Receptors”, M.B. Sporn and A.B. Roberts., eds., Springer-Verlag, New York,pp263–367 (1990).Google Scholar
- 6.D.R. Clemmons, Insulin-like growth factor binding proteins, in: “Insulin-Like Growth Factors: Molecular and Cellular Aspects”, D. LeRoith., ed., CRC Press, Boca Raton,pp151–180 (1991).Google Scholar
- 8.M.A. Bach and C.A. Bondy, Anatomy of the pituitary insulin-like growth factor system. Endocrinology (1992).(ín press)Google Scholar
- 19.R.V. Lloyd, L. Jin, K. Fields, and E. Kulig, Effects of estrogens on pituitary cell and pituitary tumor growth. Pathol. Res. Pract. 187:584 (1991).Google Scholar
- 28.W.L. Lowe Jr., S.R. Lasky, D. LeRoith and C.T. Roberts Jr., Distribution and regulation of rat insulin-like growth factor I messenger ribonucleic acids encoding alternative carboxyterminal E-peptides: evidence for differential processing and regulation in liver. Mol. Endocrinol. 2:528 (1988).PubMedCrossRefGoogle Scholar
- 35.M. Ernst, J.K. Heath, and G.A. Rodan, Estradiol effects on proliferation, messenger ribonucleic acid for collagen and insulin-like growth factor-I, and parathyroid hormone-stimulated adenylate cyclase activity in osteoblastic cells from calvariae and long bones. Endocrinology 125:825 (1989).PubMedCrossRefGoogle Scholar
- 38.F.A. Simmen, R.C. Simmen, R.D. Geisert, F. Martinat-Botte, F.W. Bazer, and M. Terqui, Differential expression, during the estrous cycle and pre-and postimplantation conceptus development, of messenger ribonucleic acids encoding components of the pig uterine insulin-like growth factor system. Endocrinology 130:1547 (1992).PubMedCrossRefGoogle Scholar