Expression of genes for oestrogen and progesterone receptors in the cervix of anoestrous ewes treated with gonadotrophin releasing hormone with or without progesterone priming.

The aim was to determine the oestrogens receptor alpha (ERα) mRNA and the binding capacity of oestrogens (ER) and progesterone receptor (PR) in the cervix of anoestrous ewes treated with gonadotrophin-releasing hormone (GnRH) with or without progesterone (P) priming, at the expected time of induced ovulation and early luteal phase. In Experiment 1, ewes were treated with P for 10 days (n=4), with nine micro-doses of GnRH followed by a GnRH bolus injection (n=4), or with P plus GnRH treatments (n=3), and tissues were harvested either without treatment (n=4), when P was removed, or 24h after the GnRH bolus injection. In Experiment 2, ewes were treated with the same GnRH or P plus GnRH treatments and tissues were harvested on Day 1 (n=12) or Day 5 (n=10) after the GnRH bolus injection. In the cranial cervix, the P treatment decreased and the GnRH treatment (after P treatment) increased the ERα mRNA, ER and PR concentrations (P<0.002). The ERα mRNA and ER concentrations were greater on Day 1, than on Day 5 in P plus GnRH treated ewes (P<0.0005). In the caudal cervix, lesser ERα mRNA, ER and PR concentrations than cranial cervix were found (P<0.0001). In conclusion, the ERα transcriptional activity and ER and PR binding capacity were strongly influenced by P and/or GnRH treatments in the cranial cervix, while the steroid receptors binding capacity remained unchanged in the caudal cervix of anoestrous ewes at the expected time of induced ovulation and early luteal phase.