GnRH agonist (buserelin) up regulates estrogen receptor α mRNA but not estrogen receptor β and progesterone receptor mRNA in bovine endometrium in vitro

Abstract

The local modulatory role of gonadotropin releasing hormone (GnRH), gonadotropin releasing hormone receptor (GnRH-R) system in regulating steroid hormone receptors at the endometrial level is still not known. Estrogen and progesterone maintain uterine functions by acting through their corresponding receptors; estrogen receptors (ERα and ERβ) and progesterone receptors (PR). We recently demonstrated GnRH-R in bovine endometrium and find the co-existence of GnRH and steroid hormone receptors in endometrium as interesting. Our objective was to determine the effect of a GnRH agonist (buserelin), on the expression of ERα, ERβ, and PR messenger RNA (mRNA) in bovine endometrium. Reproductive tracts were collected from slaughtered cows at a local abattoir, and endometrial explants were treated with buserelin (0, 200, 500, 1000 ng mL-1 respectively), GnRH antagonist-antide (500 ng mL-1) and antide + buserelin (500+200 ng mL-1) for 6 h and stored at -80°C for RNA extraction. Two micrograms of total RNA was subjected to reverse transcription polymerase chain reaction, PCR products electrophoresed (2% agrose gel); visualized and statistically analyzed. The results showed that buserelin (200 ng mL-1) increased the expression of ERα in the luteal phase endometrium. In addition, the expression of endometrial ERα was greater during the follicular than luteal phase. This up regulation of ERα mRNA in luteal phase endometrium suggests that GnRH administration may influence pregnancy in bovines. Key words: GnRH, bovine, endometrium, estrogen receptors, progesterone receptors