The percentage of pituitary gonadotropes with immunoreactive oestradiol receptors increases in the follicular phase of the ovine oestrous cycle

Abstract

During the oestrous cycle, there is an alteration in gonadotrope responsiveness to gonadotropin releasing hormone (GnRH). One cellular mechanism that may be involved in these changes at the pituitary level is the hormonal regulation of oestrogen receptor (ER) expression. Using double-label immunohistochemistry, we examined the proportion of gonadotropes, lactotropes and somatotropes with immunoreactive (ir) oestrogen receptor alpha (ERα) in pituitary sections from ewes at three stages of the ovine oestrous cycle (n = 8 per group). The percentage of ERα positive cells that also stained positive for luteinizing hormone (LH) increased in the transition from the luteal phase to the follicular ph..