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Biology of reproduction2003; 70(2); 391-399; doi: 10.1095/biolreprod.103.020800

Expression of key prostaglandin synthases in equine endometrium during late diestrus and early pregnancy.

Abstract: Luteolysis in domestic species is mediated by the release of luteolytic pulses of prostaglandin (PG) F(2alpha) by the uterus at the end of diestrus, which must be suppressed by the conceptus to permit maternal recognition of pregnancy. In many species, including the horse, both the conceptus and the endometrium also synthesize PGE(2), which may antagonize PGF(2alpha) by playing a luteotropic and/or antiluteolytic role. While the release of PGE(2) and PGF(2alpha) by the equine endometrium in late diestrus and early pregnancy has been previously studied, the underlying prostaglandin synthase gene regulatory mechanisms remain poorly defined. To resolve this issue, cyclooxygenase-2 (COX-2), microsomal PGE(2) synthase (PGES), and PGF(2alpha) synthase (PGFS) expression were examined in a series of endometrial biopsies obtained from cycling mares on Days 10, 13, and 15 postovulation, as well as from pregnant mares on Day 15. Quantification of COX-2 expression revealed significant (P < 0.01) increases in both mRNA and protein levels at Day 15 in cycling endometrium relative to other timepoints. Importantly, the level of COX-2 expression in Day 15 pregnant endometrium was found to be comparable with that observed in Day 10 and Day 13 cycling animals, suggesting that the presence of the conceptus blocks the induction of COX-2. Immunohistochemistry demonstrated that the induction of COX-2 expression on Day 15 occurs specifically in surface epithelial cells in cycling animals only. As equine PGFS had not been previously characterized, a 1380-base pair (bp) cDNA transcript was cloned by a combination of reverse transcription-PCR techniques and found to be highly homologous to bovine liver-type PGFS. The pattern of expression observed for the terminal PG synthases was distinct from that of COX-2, as PGES and PGFS mRNA and protein levels were found to be invariant throughout the timecourse and unaffected by pregnancy. Similar to COX-2, however, the PGES and PGFS proteins were found to localize mainly to the surface epithelium. Thus, this study describes for the first time the regulation and spatial distribution of COX-2, PGES, and PGFS expression in equine endometrium in late diestrus, with a marked induction of COX-2 but not of PGES and PGFS expression in uterine epithelial cells at Day 15. Furthermore, the presence of the conceptus was shown to block the induction of COX-2 expression at Day 15, suggesting an important mechanism by which it may suppress uterine PGF(2alpha) release and prevent luteolysis during early pregnancy.
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Publication Date: 2003-10-15 PubMed ID: 14561653DOI: 10.1095/biolreprod.103.020800Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article investigates the role of certain prostaglandin synthases, particularly cyclooxygenase-2 (COX-2), PGE synthase (PGES) and PGF synthase (PGFS), in the luteolysis process of horses during late diestrus and early pregnancy. Findings reveal that the presence of the conceptus may inhibit the release of prostaglandin PGF2alpha, a compound that induces luteolysis, by blocking the induction of COX-2 expression in the endometrium.

Study Explanation and Methodology

  • The research aims to uncover the molecular processes related to prostaglandin synthesis in the horse’s endometrium during late diestrus and early pregnancy, with a focus mainly on cyclooxygenase-2 (COX-2), PGE synthase (PGES) and PGF synthase (PGFS).
  • The scientists were interested in these synthases because they play crucial roles in the production of prostaglandins (including PGF2alpha and PGE2), which are suspected to be key regulators of maternal recognition during early pregnancy and luteolysis during diestrus.
  • The research was conducted using endometrial biopsies taken from cycling mares on Days 10, 13, and 15 postovulation to observe any changes in synthase gene expression and protein levels. This was also compared with endometrial biopsies from pregnant mares on Day 15.

Findings

  • Results showed that there was a significant increase in both COX-2 mRNA and protein levels in the cycling endometrium specifically on Day 15, which wasn’t observed at other time-points or in the Day 15 pregnant endometrium.
  • This increase in COX-2 expression was found to be specific to surface epithelial cells and evidence suggested the presence of a conceptus – a fertilized ovum – blocked COX-2 induction.
  • The study confirms the importance of COX-2 in PG synthesis, as it is involved in the conversion of arachidonic acid to PGH2, the precursor for other PGs, including PGF2alpha, which is directly involved in luteolysis.
  • In contrast, the levels of PGES and PGFS mRNA and proteins didn’t significantly change throughout the time of study or in reaction to pregnancy, an indication that these synthases are not as reactionary as COX-2 and might play a basal role in the synthesis of PGs.

Importance of the Findings

  • This study provides new insights into the molecular mechanics of horse reproduction, in particular, the role of COX-2 in luteolysis and the inhibition of this enzyme by the conceptus to allow early pregnancy.
  • These findings could also be applied to other species, providing a more precise understanding of how various molecular processes contribute to maintaining and terminating pregnancy.

Cite This Article

APA
Boerboom D, Brown KA, Vaillancourt D, Poitras P, Goff AK, Watanabe K, Doré M, Sirois J. (2003). Expression of key prostaglandin synthases in equine endometrium during late diestrus and early pregnancy. Biol Reprod, 70(2), 391-399. https://doi.org/10.1095/biolreprod.103.020800

Publication

Biology of reproduction
ISSN: 0006-3363
NlmUniqueID: 0207224
Country: United States
Language: English
Volume: 70
Issue: 2
Pages: 391-399

Researcher Affiliations

Boerboom, Derek
  • Centre de Recherche en Reproduction Animale, Faculté de Médecine, Université de Montréal, Canada.
Brown, Kristy A
    Vaillancourt, Denis
      Poitras, Pierre
        Goff, Alan K
          Watanabe, Kikuko
            Doré, Monique
              Sirois, Jean

                MeSH Terms

                • Animals
                • Cloning, Molecular
                • Cyclooxygenase 2
                • Diestrus / physiology
                • Endometrium / enzymology
                • Female
                • Gene Expression Regulation, Enzymologic
                • Horses
                • Hydroxyprostaglandin Dehydrogenases / genetics
                • Hydroxyprostaglandin Dehydrogenases / metabolism
                • Immunohistochemistry
                • Intramolecular Oxidoreductases / genetics
                • Intramolecular Oxidoreductases / metabolism
                • Isoenzymes / genetics
                • Isoenzymes / metabolism
                • Male
                • Pregnancy
                • Pregnancy, Animal / physiology
                • Prostaglandin-E Synthases
                • Prostaglandin-Endoperoxide Synthases / genetics
                • Prostaglandin-Endoperoxide Synthases / metabolism
                • RNA, Messenger / analysis

                Citations

                This article has been cited 17 times.
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