Glucocorticoid Receptors in Rat Thymus Cells

摘要: Summary Studies of binding glucocorticoids to rat thymus cells in vitro demonstrate two forms binding: (a) Specific binding, which is well correlated with glucocorticoid activity, saturates at high physiological concentrations, and characterized by slow association dissociation. appears represent receptors. With cortisol no metabolic transformation precedes this association. (b) Non-specific correlates nonpolarity interfacial does not saturate, rapid all steroids tested the major fraction. It distributed throughout cell including nucleus, accounting for well-known nonspecific effects vitro. ATP or some related substance may be necessary specific whole cells. A competitor cortexolone, blocks hormonal activity cortisol. If are disrupted hypotonic shock 1.5 mM MgCl2 after incubation 20 °C 37 most specifically bound hormone sediments nuclei. But 3 mainly supernatant. For convenience supernatant fraction referred as “cytoplasmic”. Cortisol both nuclear “cytoplasmic” fractions macromolecules. These “receptors” part proteins. The properties – specificity, saturation, dissociation rates isolated receptors, can extracted from that have been preexposed cortisol, similar those characteristic °C, showing displays intrinsic receptor complexes. receptors rapidly transferred nucleus even presence excess unlabelled indicating formation cytoplasmic complex an obligatory step. do appear ‘carriers’ since freely permeable glucocorticoids. suggested directs site increasing its affinity and/or releasing it initial site. To initiate probably has attached active molecule, cortexolone a steroid-receptor formed but initiated.