ABSTRACT
This chapter describes the radioautographic techniques that have been used in the study of estrogen receptors. It discusses the localization of cytosol-nuclear estrogen receptors in the rat uterus and analyzes the differences in receptor level regulation in the various target cell types. Estrogen action in the rat uterus has frequently been taken as a model for the investigation of the mechanisms of steroid hormone action. Radioautography is a very sensitive technique for the study of radioactive substances in tissues that can detect up to a few hundred labeled molecules per cell. A quantitative evaluation of radioautograms of sections that have been incubated with different concentrations of labeled steroids can be used for the evaluation of the affinity of the hormone for its receptors. Each steroid hormone receptor is specific for its high-affinity binding to its own class of hormones. Estrogen binding by the nuclei of uterine cells has classically been assumed to reflect the existence of cytosol-nuclear receptors.
