An immunohistochemical study on the regulation of estrogen receptor a by estradiol in the endometrium of the immature ewe

The effects of estradiol-17 beta (E2) on the expression of estrogen recepto r alpha (ER alpha) in stromal and epithelial cells of endometrium in prepub ertal lambs were investigated. Twenty three-month-old lambs were treated or not treated with one, two or three i.m. injections of E2 (1 mug.kg(-1)) in corn oil at intervals of 24 h. Lambs were slaughtered 12 or 24 h after the last injection. An immunohistochemical technique was used to visualize ER alpha immunostaining which was then analyzed quantitatively by a computer i maging analysis system. Seven endometrial compartments defined by cell type and location were analyzed separately. Positive staining of ER alpha was s een in the nuclei of stromal and epithelial cells. Glandular epithelium loc ated next to the myometrium was stained more intensely than that next to th e luminal epithelium and this phenomenon was maintained during treatment. S ignificantly less immunostaining was found in stromal cells 12 and 24 h aft er the first injection compared to the control group. A similar pattern was found in the glandular epithelium, although the decrease was more pronounc ed and the restoration of ER alpha was faster. This study shows that E2 tre atment down regulates ER alpha in the endometrium temporarily in both strom al and epithelial cells, but the characteristics of this effect seems to be cell type specific.