Cellular Localization of Estrogen and Progestin Receptors in the Macaque Reproductive System

Summary

The past few years have seen a dramatic change in our understanding of the intracellular localization of steroid receptors. Previous lines of evidence had suggested that estrogen and progestin receptors were localized in the cytoplasm in the absence of ligand and that ligand binding to receptor provoked translocation of the steroid-receptor complex to the nucleus. Various techniques, including immunocytochemistry in cryosections, have revealed that most steroid receptors are nuclear proteins whether occupied by steroids or not. In addition, most studies of the hormonal regulation of receptors have been done on extracts of homogenates of whole tissues. Generally this work has indicated that estrogens increase the amount of both the estrogen and progestin receptors and that progestins suppress the level of both receptors. Immunocytochemistry has now revealed that these regulatory processes differ markedly among the different cell types of the reproductive tract. In addition there is new immunocytochemical evidence of the importance of stromal-epithelial interactions in steroid hormone action. Steroid-induced epithelial growth and/or differentiation can occur in tissues where steroid receptors are only detectable in the stromal cells. In this review, immunocytochemical evidence for the nuclear localization of estrogen and progestin receptors, for the variation in receptor regulation in different cell types and for the possible hormone action will be presented. All data will be based on experimental studies of the reproductive system of male and female nonhuman primates.