Differential immunolocalization of estrogen receptor alpha and beta in ratovary and uterus

In order to investigate the localization of estrogen receptor (ER) alpha an d ER beta in the reproductive organs in the rat, polyclonal antibodies were raised to each specific amino acid sequence. The Western blot with anti-ER alpha antibody showed a 66 kDa band in rat ovary and uterus, while that wi th anti-ER beta antibody detected a 55 kDa band in rat ovary, uterus and pr ostate. The ligand-independent nuclear localization of the two receptors wa s verified by immunocytochemistry. By immunohistochemistry, the nuclei of g landular and luminal epithelial cells in the uterus were stained with anti- ER alpha antibody, whereas only the nuclei of glandular epithelium cells we re stained with anti-ER beta antibody. In rat ovary, positive signals were shown with anti-ER beta antibody in the nuclei of granulosa cells. No speci fic immunostaining was observed with anti-ER alpha antibody. Although ER be ta was immunostained at the proestrous, metestrous and diestrous stages, th e immunoreactivity of ER beta was hardly detected at the estrous stage in r at ovary. Thus, we show differential expression of ER alpha and ER beta in rat uterus and ovary at the protein level, which may provide a clue for und erstanding the roles of the two receptors in reproductive organs.