Oxytocin stimulated release of PGF2α and its inhibition by a cyclooxygenase inhibitor and an oxytocin receptor antagonist from equine endometrial cultures

Uterine inflammation results in a poor uterine environment and early embryonic loss in the mare due to an inhibition of maternal recognition of pregnancy caused from increased prostaglandin F2α (PGF2α). Oxytocin binds to endometrial cell receptors to activate prostaglandin synthesis. An oxytocin receptor antagonist (Atosiban) and a cyclooxygenase inhibitor (indomethacin) both decrease PGF2α production. The aim of this study was to evaluate the in vitro effects of Atosiban and indomethacin on equine uterine prostaglandin secretion. Equine endometrial explants were harvested on day two of behavioral estrus. Endometrial explant cultures were challenged with oxytocin (250 nM) and PGF2α concentrations were measured over time. Explants were also cultured with Atosiban and indomethacin for 6 h to determine the influence on PGF2α secretion. When endometrial explants were challenged with oxytocin, PGF2α concentrations were greater (P < 0.0001) at each time point over the 24 h of culture as compared to controls. Oxytocin failed (P < 0.001) to elicit PGF2α release in explants cultured with either Atosiban or indomethacin. These findings show equine endometrial explants can be stimulated with oxytocin to increase secretion of PGF2α and this secretion can be inhibited through an oxytocin receptor antagonist and a Cox inhibitor, suggesting that this response to oxytocin involves an oxytocin receptor mediated event that activates the prostaglandin synthesis cascade through cyclooxygenase. Furthermore, this data suggests a role for the use of these inhibitors in vivo to decrease uterine PGF2α secretion and prevent early luteal regression and embryonic loss.