The expression of ERα, OTR, cPLA2, COX-2, and PPARγ in the cervix of the ewe during the estrous cycle

The ovine cervix relaxes at estrus allowing easier entry of spermatozoa into the uterus. The mechanism responsible for this relaxation is not fully elucidated and we hypothesized that cervical relaxation at estrus is induced by ovarian and pituitary hormones stimulating the local production of prostaglandin E-2 Via a biosynthetic pathway involving a number Of mediators including oxytocin, phospholipase A(2) (cPLA(2)), cyclooxygenase-2 (COX-2), and peroxisome proliferator-activated receptor gamma (PPAR gamma). The aim of this study was to investigate the cervical expression of estradiol receptor alpha (ER alpha), oxytocin receptor (OTR), cPLA(2), COX-2, and PPAR gamma at three stages of the estrous cycle (the luteal phase and two times during the follicular phase, just before and just after the LH surge). An experiment was conducted during the breeding season, in 25 ewes to test this hypothesis. Samples of cervical tissue were collected from groups of ewes at three stages of the estrous cycle: the luteal (N = 8), pre-LH surge (N = 8), and post-LH surge (N = 9) stages. Cervical tissue from uterine, mid, and vaginal regions of the cervix were analyzed by Western immunoblot analysis for ER alpha, OTR, cPLA(2), COX-2, and PPAR gamma. The results showed that the levels of all five proteins were lowest during the luteal phase of the estrous cycle in all regions of the cervix. The levels of all except cPLA(2), increased significantly during the pre-LH surge stage. The levels of cPLA(2) and ER alpha increased in the post-LH surge stage and those for OTR and PPARy were unchanged and those for COX-2 were lower. These data show that the cervical levels of all five of the intermediates in the synthesis of prostaglandin E-2 that were examined in this study were higher in the pre- and post-LH surge stages compared with the luteal phase of the estrous cycle and these findings are consistent with our hypothesis. (C) 2013 Elsevier Inc. All rights reserved.