Ovine placental lactogen binds specifically to endometrial glands of the ovine uterus
Date
2002
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Texas A&M University
Abstract
A hormonal servomechanism has been proposed to regulate differentiation and function of the endometrial glandular epithelium (GE) in the ovine uterus during pregnancy that involves sequential actions of estrogen, progesterone, ovine interferon tau (IFN[T]), placental lactogen (oPL), and placental growth hormone (oGH). The biological actions of oPL in vitro are mediated by homodimerization of the PRL receptor (oPRLR) as well as heterodimerization of the oPRLR and oGH receptor (oGHR). The objectives of this study were to: (1) determine effects of intrauterine oPL, oGH and their combination on endometrial histoarchitecture and gene expression; (2) localize and characterize binding sites for oPL in the ovine uterus in vivo using an in situ ligand binding assay; and (3) determine temporal and spatial alterations in STAT 1, 3 and 5 expression in the pregnant ovine uterus. Intrauterine infusion of oPL and/or oGH following IFN[T] into ovariectomized ewes treated daily with progesterone differentially affected endometrial gland number and expression of uterine milk proteins and osteopontin. However, neither hormone affected PRLR, IGF-I or IGF-II mRNA levels in the endometrium. A chimeric protein of placental secretory alkaline phosphatase (SEAP) and oPL (SEAP-oPL) was used to identify and characterize binding sites for oPL in frozen sections of interplacentomal endometrium from pregnant ewes. Specific binding of SEAP-oPL was detected in the endometrial GE on Days 30, 60, 90, and 120 of pregnancy. In Day 90 endometrium, SEAP-oPL binding to the endometrial GE was displaced completely by oPL and oPRL, but only partially by oGH. Binding experiments using the extracellular domain of the oPRLR also showed that iodinated oPL binding could be competed by oPRL and oPL, but not by oGH. Collectively, results indicate that oPL binds to receptors in the endometrial glands and that PRL is more effective than GH for competing these binding sites. Thus, effects of oPL on the endometrial glands may be mediated by both PRLR and GHR.
Description
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Includes bibliographical references (leaves 90-115).
Issued also on microfiche from Lange Micrographics.
Includes bibliographical references (leaves 90-115).
Issued also on microfiche from Lange Micrographics.
Keywords
physiology of reproduction., Major physiology of reproduction.