Differential immunolocalization of estrogen receptor alpha and beta in rat ovary and uterus

In order to investigate the localization of estrogen receptor (ER) alpha and ERbeta in the reproductive organs in the rat, polyclonal antibodies were raised to each specific amino acid sequence. The Western blot with anti-ERalpha antibody showed a 66 kDa band in rat ovary and uterus, while that with anti-ERbeta antibody detected a 55 kDa band in rat ovary, uterus and prostate. The ligand-independent nuclear localization of the two receptors was verified by immunocytochemistry. By immunohistochemistry, the nuclei of glandular and luminal epithelial cells in the uterus were stained with anti-ERalpha antibody, whereas only the nuclei of glandular epithelium cells were stained with anti-ERbeta antibody. In rat ovary, positive signals were shown with anti-ERbeta antibody in the nuclei of granulosacells. No specific immunostaining was observed with anti-ERalpha antibody. Although ERbeta was immunostained at the proestrous, metestrous and diestrous stages, the immunoreactivity of ERbeta was hardly detected at the estrous stage in rat ovary. Thus, we show differential expression of ERalpha and ERbeta in rat uterus and ovary at the protein level, which may provide a clue for understanding the roles of the two receptors in reproductive organs.