A modified immunohistochemical procedure for the detection of estrogen receptor in mouse tissues

A horseradish peroxidase (HRP) labeled antibody method was developed for use with a monoclonal antibody to detect estrogen receptor (ER) in mouse tissue. Combined use of HRP labeled F(ab')2 fragment absorbed with mouse liver protein to minimize background staining and imidazol-DAB reaction gave the most reliable and sensitive immunostaining. The method was applied to uterine, vaginal, pituitary and liver tissues in ovariectomized adult mice. In uterus and vagina, ER was recognized in nuclei of epithelial cells, stromal cells and smooth muscle cells of the muscle layer and blood vessels. Liver tissue showed positive nuclear immunostaining in parenchymal cells; however, no reaction was present in endothelial cells, Kupffer cells, bile ductal cells, and smooth muscle cells of blood vessels. ER was localized in the nuclei of anterior pituitary cells while weak reaction was also recognized in cells of the intermediate lobe. No staining was detected in the posterior pituitary. Results demonstrate that both occupied and unoccupied ER are localized in the cell nucleus from several target tissues. Weak immunostaining in samples could not be enhanced by multiple procedures. It is suggested that nuclear ER is partially hidden by nuclear components such as nucleic acid and chromatin proteins.