Immunocytochemical Localization of Estrogen Receptors in the Macaque Reproductive Tract with Monoclonal Antiestrophilins*

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Abstract
Monoclonal antibodies to the estrogen receptor (anti-ER) were used to develop an immunocytochemical method to detect ER in frozen sections of the macaque reproductive tract. Specific nuclear, but not cytoplasmic, staining occurred with 2 different methods: direct, in which an antiestrophilin-horseradish peroxidase conjugate was used as the 1st antibody, and indirect, in which a mixture of antiestrophilins was used in the 1st incubation step. Nuclear staining was absent when various control antibodies replaced the anti-ER. In uteri from spayed monkeys treated with estradiol (E2) for 14 days, nuclear staining was always present. In uteri from similar animals treated for an additional 14 days with E2 and progesterone, nuclear staining was almost completely absent. Mean endometrial nuclear ER levels, measured by an exchange assay, were 5-fold greater in the E2-treated than in the E2- plus progesterone treated group. In addition, when samples of estrogenized uterus and oviduct were incubated for 60 min in vitro with 100 nM E2, the intensity of nuclear staining increased in parallel with an increase in the concentration of nuclear ER. The nuclei of stromal, smooth muscle, and epithelial cells of the estrogenized oviduct, cervix, and vagina as well as smooth muscle cells of the estrogenized myometrium were also receptor positive. Nontarget tissues, such as duodenum, colon, esophagus, and skeletal muscle, contained no cells that showed specific nuclear staining. Some staining of cytoplasmic and extracellular components occurred in all preparations. These latter reactions were nonspecific, because they were present in many nontarget tissues or when control antibodies replaced the anti-ER. With current methods, only nuclear ER can be reliably localized in frozen sections of monkey tissues with monoclonal antiestrophilins.