[The localization of estrogen receptor (ER) in target tissues as visualized by immunoperoxidase method using anti-ER antibody].

It is very important to detect the intracellular distribution and dynamics of estrogen receptor (ER) in order to make the mechanisms of estrogen action clear. In a recent report, monoclonal antibodies localized ER only in the nucleus of target cells under both the presence and absence of estrogen. We purified cow and human uterine ER and induced specific polyclonal anti-ER antibodies. In this report, the specificity of immunological reactivity of anti-ER antibodies was examined, and the distribution of ER in the target tissues was detected by the indirect immunoperoxidase method. The specific staining was observed in the nucleus and cytoplasm of the endo- and myometrium of cow, rat and human uterus. In the nontarget organs, such as kidney and muscle, the specific staining was not detected. The cytoplasm of MCF-7 cells and immature rat uterine tissues were mainly stained without estrogen; however, the nuclear staining increased obviously after the estrogen priming. The cytoplasmic and/or nuclear staining was positive in 63% of 21 human breast cancer cases. This immunohistochemical assay (IHC) method of ER measurement was compared with the DCC assay method, a biochemical assay based on hormone binding ability. The concomitant positivity or negativity in DCC and IHC were observed as 61.9% (13 cases) or 19.0% (4 cases), respectively. Therefore, these two methods showed the same assay results in 81.0% of human breast cancer tissues.