Haslam S Z, McBlain W A, Shyamala G
J Recept Res. 1981;2(5-6):435-51. doi: 10.3109/107998981809038877.
Normal mammary glands of mice contain both progesterone and glucocorticoid receptors and the levels of both these receptors are modulated as a function of development. Measurement of progesterone receptors using the synthetic progestin, R5020, has led to conflicting data both with regard to the presence of progesterone receptor during certain developmental stages of the mammary gland and the ability of the glucocorticoids to compete for specific R5020 binding sites. In this report we have identified experimental conditions which allow for the separate measurements of the progesterone and glucocorticoid receptors in the same cytosol. If sulfhydryl reducing agents such as dithiothreitol are excluded from the assay buffer, R5020 binds to only a single class of high affinity sites in mammary cytosol of virgin mice and these binding sites exhibit a strict steroid specificity characteristic of progesterone receptors. In contrast, if dithiothreitol is included in the buffers, R5020 binds not only to the high affinity sites but also to certain saturable lower affinity sites; these lower affinity sites for R5020 also bind glucocorticoids such as dexamethasone. These findings should facilitate more accurate quantitation of both progesterone and glucocorticoid receptors in normal and neoplastic tissues and also be applicable to studies on the mechanism(s) of progesterone action.
小鼠的正常乳腺含有孕酮受体和糖皮质激素受体，并且这两种受体的水平会随着发育过程而受到调节。使用合成孕激素R5020来测量孕酮受体，在乳腺的某些发育阶段孕酮受体的存在情况以及糖皮质激素竞争特定R5020结合位点的能力方面，都得出了相互矛盾的数据。在本报告中，我们确定了一些实验条件，能够在同一细胞溶质中分别测量孕酮受体和糖皮质激素受体。如果在测定缓冲液中不使用诸如二硫苏糖醇之类的巯基还原剂，R5020只会与未交配小鼠乳腺细胞溶质中的一类高亲和力位点结合，并且这些结合位点表现出孕酮受体严格的类固醇特异性特征。相反，如果在缓冲液中加入二硫苏糖醇，R5020不仅会与高亲和力位点结合，还会与某些可饱和的低亲和力位点结合；这些R5020的低亲和力位点也会结合诸如地塞米松之类的糖皮质激素。这些发现应该有助于更准确地定量正常组织和肿瘤组织中的孕酮受体和糖皮质激素受体，也适用于孕酮作用机制的研究。
