HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 69/5/1743    most recent biolreprod.103.018812v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Saint-Dizier, M. Articles by Combarnous, Y. Search for Related Content PubMed PubMed Citation Articles by Saint-Dizier, M. Articles by Combarnous, Y. Agricola Articles by Saint-Dizier, M. Articles by Combarnous, Y.

Expression and Binding Activity of Luteinizing Hormone/Chorionic Gonadotropin Receptors in the Primary Corpus Luteum During Early Pregnancy in the Mare¹

Unité de Physiologie de la Reproduction et des Comportements,³ UMR 6073 INRA-CNRS-Université F. Rabelais de Tours, 37380 Nouzilly, France

Luteal steroids are necessary to maintain the first 70–90 days of pregnancy in the mare. At 35 days postovulation, the resurgence of the primary corpus luteum (CL) coincides with the secretion of the fetal hormone eCG. In order to study the responsiveness of the primary CL to eCG, we have examined levels of luteal equine LH/CG receptors (eLH/CG-R) mRNAs by Northern blot analysis and measured concentrations of eLH/CG binding sites on luteal membranes using ¹²⁵I-eLH saturation binding assays at three stages of gestation: before the onset of eCG secretion (Days 14–31), from onset to maximum eCG secretion (Days 38–62), and during decline of eCG secretion (Days 83–101). Multiple transcripts of eLH/CG-R (7, 5.7, 4.9, 3.9, 2.8, 1.8, 0.6 kilobase [kb]) were identified in the primary CL at all stages examined. Three of them (5.7, 2.8, 0.6 kb) coded for truncated eLH/CG-R lacking the transmembrane domain. The relative intensities of the four major transcripts tended to decrease (5.7 and 3.9 kb) or were steadily expressed (7 and 1.8 kb) during pregnancy. The affinity of eLH/CG binding sites did not change during pregnancy whereas the number of eLH/CG binding sites decreased significantly after the onset of eCG secretion. Nevertheless, levels of binding sites were still at 44.6% (Days 38–62) to 24.7% (Days 83–101) of those measured before the onset of eCG secretion. Taken together, the presence of eLH/CG-R mRNAs and of a substantial part of eLH/CG binding sites with high affinity suggest that the primary CL still expresses a high number of eLH/CG-R and remains responsive to eCG during early pregnancy.

¹ M.S.-D. was supported by a fellowship from the Institut National de la Recherche Agronomique and the Région Centre.

² Correspondence: Marie Saint-Dizier, Equipe Hypophyse, Station Physiologie de la Reproduction et du Comportement, Institut National de la Recherche Agronomique (INRA), 37380 Nouzilly, France. FAX: 33 2 47 42 77 43; dizier{at}tours.inra.fr

³ Current Address: Equitechnique, Le Mesnil Vicomte, 61240 Le Merlerault, France

This article has been cited by other articles:

				M. Saint-Dizier, F. Foulon-Gauze, F. Lecompte, Y. Combarnous, and M. Chopineau Cloning and functional expression of the equine luteinizing hormone/chorionic gonadotrophin receptor J. Endocrinol., December 1, 2004; 183(3): 551 - 559. [Abstract] [Full Text] [PDF]

				M. Saint-Dizier, M. Chopineau, J. Dupont, and Y. Combarnous Expression of the full-length and alternatively spliced equine luteinizing hormone/chorionic gonadotropin receptor mRNAs in the primary corpus luteum and fetal gonads during pregnancy Reproduction, August 1, 2004; 128(2): 219 - 228. [Abstract] [Full Text] [PDF]