STRUCTURAL AND FUNCTIONAL CHARACTERIZATION OF PLACENTAL LACTOGENS

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The mouse placenta produces two placental lactogens (PLs); mPL-I and mPL- II. The long term objectives of the project are to understand the functions of these hormones in various target tissues and to understand what regulates their production and concentrations in the fetal and maternal blood. Although relatively little is known about the biological activities and regulation of secretion of PLs in various species, it is clear that PLs participate in several important processes during pregnancy. Investigating the physiology of PLs will contribute to a better understanding of the processes that influence fetal health and survival; during pregnancy. These studies are a continuation of previous work in this laboratory on the biological and regulation of secretion of mPL-I and mPL-II. Several experiments include examining the regulation of secretion of proliferin (PLF) and PLF-related protein (PRP), which are proteins that are structurally similar to the PLs and are also produced by the mouse placenta. The specific aims of this project are: (1) The primary structure of calcyclin, a stimulator of mPL-II secretion will be determined. The protein will be localized in the conceptus by in situ hybridization, and the presence of binding sites for decidual calcyclin in the placenta will be assessed. Effects of decidual calcyclin on PL-I, PLF and PRP secretion will be examined in vivo. (2) Effects of epidermal growth factor, transforming growth factors alpha and beta, tumor necrosis factor-alpha, interleukin (IL)-beta, and IL-6 alone and in combinations, will be determined on giant cell differentiation and on mPL-I, mPL-II, PLF and PRP secretion by placental cells from various days of pregnancy. The sites of production of these agents in the conceptus will be determined by in situ hybridization. (3) The structure of the genes for mPL-I and mPL-II will be determined, and the promoter region will be examined for the presence of known response elements. Putative regulators of mPL-I and mPL-II expression identified in this way will be examined in vitro and in vivo for effects on mPL-I and mPL-II secretion. (4) A putative stimulator of mPL-I secretion produced by the pituitary gland will be characterized and if it appears to be novel, it will be purified and characterized. (5) An inhibitor of prolactin secretion produced by the placenta will be purified. Its interaction with mPL-I and mPL-II in regulating prolactin secretion will be examined in vitro. (6) A novel 29K insulin-like growth factor binding protein (IGBP) whose production is induced by mPLs will be purified and its primary structure will be determined. The liver will be examined for the presence of 29K IGFBP. The gestational profile of 29K IGFBP in liver and mammary gland will be determined. Regulation of 29K IGFBP by mPL-I and mPL-II in liver and mammary gland will be examined. (7) Proteins regulated by mPL-I and mPL-II in maternal liver will be identified.