Differential regulation of insulin-like growth factor binding protein-1 and -2 by insulin in the baboon ( Papio anubis )
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Differential regulation of insulin-like growth factor binding protein-1 and -2 by insulin in the baboon (Papio anubis) endometrium Steven D Fleming1, Asgerally T Fazleabas*2 and Stephen C Bell3 Address: 1Department of Obstetrics and Gynaecology, University of Sydney, NSW 2145, Australia, 2Department of Obstetrics and Gynecology (MC808), College of Medicine, University of Illinois at Chicago, Illinois 60612-9998, USA and 3Department of Obstetrics and Gynaecology, University of Leicester, Leicestershire LE2 7LE, UK Email: Steven D Fleming - [email protected]; Asgerally T Fazleabas* - [email protected]; Stephen C Bell - [email protected] * Corresponding author
Published: 31 January 2008 Reproductive Biology and Endocrinology 2008, 6:6
doi:10.1186/1477-7827-6-6
Received: 20 August 2007 Accepted: 31 January 2008
This article is available from: http://www.rbej.com/content/6/1/6 © 2008 Fleming et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract Background: The purpose of this study was to examine the effect of insulin on expression and synthesis of IGFBP-1 and IGFBP-2 in the baboon endometrium in vitro. Methods: Baboon endometrial explants collected from cycling, ovariectomized, steroid-treated, simulated-pregnant and pregnant animals were cultured for 48 h in the presence or absence of insulin, with or without estradiol, progesterone and hCG. Results: Insulin clearly inhibited IGFBP-1 production and mRNA expression in a time- and dosedependent manner, whereas IGFBP-2 synthesis was not significantly affected. The inhibitory effects of insulin on IGFBP-1 were more evident in explants of non-pregnant tissue or tissue away from the implantation site. In the absence of insulin, synthesis of IGFBP-1 was induced in explants with low levels of de novo synthesis whereas IGFBP-2 synthesis was inhibited. This effect was potentiated by steroids and hCG in the explant cultures. Conclusion: Insulin differentially regulates endometrial IGFBP-1 and IGFBP-2 secretion in the baboon.
Background The insulin-like growth factor binding proteins (IGFBPs) include IGFBP-1 and IGFBP-2 that are non-glycosylated, low molecular weight IGFBPs that have a homologous amino acid sequence. They are important modulators of insulin-like growth factor (IGF) bioactivity. In this respect, IGFBP-1 and IGFBP-2 may potentiate the binding of IGFs to target cells via integrin receptors by virtue of the fact that both IGFBP-1 and IGFBP-2 have Arg-Gly-Asp (RGD) sequences at their C-terminus. The IGFs, IGF-1 and IGF-2, are mitogens that are involved in the regulation of
endometrial cell proliferation, differentiation and apoptosis. Indeed, during the menstrual cycle the mitogenic effects of estrogen, balanced by the differentiating properties of prog
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