Diestrus administration of oxytocin prolongs luteal maintenance and reduces plasma PGFM concentrations and endometrial COX-2 expression in mares

L. Keith, B. A. Ball, K. Scoggin, A. Esteller-Vico, E. M. Woodward, M. H.T. Troedsson, E. L. Squires

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The objectives were to: (1) evaluate the efficacy of varying intervals of oxytocin administration in preventing luteolysis in mares; (2) examine PGF release in mares experiencing prolonged diestrus secondary to oxytocin treatment; and (3) evaluate the endometrial expression of oxytocin receptor, estrogen receptor α, and prostaglandin synthesis enzymes after oxytocin administration. In experiment I, mares received oxytocin (60 IU, im) daily on Days 8 to 10, 8 to 12, or 8 to 14 postovulation, and control mares received sterile saline. Prolongation of diestrus was defined by elevation of serum progesterone >1.0 ng/mL through Day 30 postovulation. The proportion of mares experiencing prolonged cycles increased (P < 0.01) as the number of days of oxytocin administration increased. Oxytocin administration on Days 8 to 10, 8 to 12, and 8 to 14 prolonged luteal maintenance in 3/7, 4/7, and 6/7 mares respectively, compared with 0/7 control mares. Treated mares with prolonged diestrus had lower (P < 0.05) plasma PGFM concentrations at Day 16 than did mares with normal diestrus periods. In experiment II, endometrial biopsies from mares treated with oxytocin from Days 8 to 14 postovulation (N = 6) had reduced cyclooxygenase-2 expression (P < 0.05) compared with control mares (N = 6) as determined by quantitative reverse transcription polymerase chain reaction and immunohistochemical staining. Oxytocin administration prolonged luteal maintenance in mares, with an increasing number of mares responding to treatment as the number of days of oxytocin administration was increased beyond Day 8 postovulation. Luteal maintenance in mares was also associated with decreased plasma PGFM concentrations and reduced endometrial cyclooxygenase-2 expression.

Original languageEnglish
Pages (from-to)616-624
Number of pages9
JournalTheriogenology
Volume79
Issue number4
DOIs
StatePublished - Mar 1 2013

Bibliographical note

Funding Information:
Supported by the Kentucky Equine Drug Research Council , the Albert G. Clay Endowment , and the Geoffrey C. Hughes Foundation .

Keywords

  • Cyclooxygenase 2
  • Endometrium
  • Equine
  • Luteolysis
  • Oxytocin
  • Oxytocin receptor

ASJC Scopus subject areas

  • Small Animals
  • Food Animals
  • Animal Science and Zoology
  • Equine

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