Evidence for Uterine Horn Differences in Local Concentrations of Oxytocin, Oxytocin Receptor and Prostaglandin F_2α during the Estrous Cycle and Early Pregnancy in Cows

Abstract

ContentsThe current study investigated the endometrial concentration of oxytocin (OT), oxytocin receptors (OT-R) and prostaglandin Fzc, (PGF2?) ipsilateral and contralateral to the corpus luteum (CL) and their inter-relationships during the estrous cycle and early pregnancy. Reproductive tracts of 45 Holstein COWS collected from the slaughterhouse were used. Estimation of the stages of the estrous cycle was determined, based on CL characteristics and progesterone P4 levels. The luteal stage was characterized by higher OT levels in the ipsilateral horn than contralateral horn, while OT-R and PGFzl levels were low and similar in both uterine horns. At follicular stage, thc ipsilateral horn showed significantly higher concentrations of OT, OT-R and PGF2, than the contralateral horn. At post-ovulation, OT levels remained high and significantly higher in the ipsilateral horn. The OT-R and PGF2, levels decreased to a certain level but were not significantly different from their levels at the follicular stage, and no difference was found between horns. At early pregnancy, OT levels were low, OT-R levels were significantly lower in the ipsilateral than in the contralateral horn. and PGF2, decreased, but the levels were higher than at luteal phase. The results indicate clear stage-dependent changes of endocrine parameters within ipdateral and contralateral horn in relation to the CL and suggest that the horn adjacent to CL is more active, sensitive and responsive to the cause and effect of luteolysis, supporting the concept of a utero-ovarian local regulating mechanism. Further, the significantly low OT-R in the ipsilateral horn suggests a local effect of the CL or the embryo. Inhalt Unterschiedliche lokale Konzentrationen von Oxytocin, Oxytocin-Rezeptor und Prostaglandin FZx in den Uterushiirnern bei zyklischen und friihtragenden KuhenIn der vorleigenden Untersuchung wurde die endometrische Konzentration von Oxytocin (OT), Oxytocin-Rezeptor (OT-R) und Prostaglandin F2, (PGF2,) im ipsi-und kontralateralen Horn zum Corpus luteum (CL) untersucht und die Abhlngigkeit wahrend der Brunst und der friihen Trachtigkeit bestimmt. Es wurden Genitalorgane (Schlachtorgane) von 45 HolsteinKiihen venvendet. Die Schatzung des Zyklusstadiums basicrte auf den Merkmalen der Gelbkorper-und der P3 Level. In der Gelbkorperphase waren charakteristisch hohcre OT-Spiegel im ipsilateralen Horn als im kontralateralen Horn zu finden, wohingegen OT-R und PGF2, in beiden Hornern gering waren. In der Follikelphase wies das ipsilaterale Horn im Vergleich zum kontralateralen signifikant hohere Konzentrationen von OT, OT-R und PGF2, auf. Postovulatorisch verblieben die OTWerte auf hoherem Niveau und waren im ipsilateralcn Horn signifikant hoher. OT-R-und PGF2,-Werte sanken bis auf ein bestimmtes Niveau, aber waren nicht signifikant unterschiedlich zu den entsprechenden Werten der Follikelphase. Zwischen den beiden Hornern wurden keine Unterschiede gefunden. Wahrend der friihen Trachtigkeit waren die OTWerte niedrig, die OT-R-Level signifikant geringer im...

Regulatory effect of steroid hormones and fetal tissues on expression of oxytocin receptor in the endometrium of late pregnant ewes

“…Low expression of oxytocin receptors appears in the ovine endometrial luminal epithelium after about 21 days of pregnancy, when interferon production ceases, and remains until parturition when further upregulation occurs (Wathes et al, 1996a;Wu et al, 1996). Although progesterone may be responsible for the suppression ol oxvtoein receptors throughout pregnancy, there is evidence to indicate that the fetus also has a local influence on oxytocin receptor expression (Cerbito et al, 1997;Parry et al, 1997). Unknown factors in addition to progesterone secreted from luteal tissues have also been implicated in inhibiting the expression of oxytocin receptors in the endometrium of cyclic sheep .…”