Demonstration of steroid specific hormone receptors by chromatography

Activation of mineralocorticoid agonist and antagonist specific receptors from rat kidney

The kinetics of saturation, as well as of denaturation, confirm the existence of two distinct mineralocorticoid receptor populations one each for the agonist aldosterone (MR2) and the antagonist RU 26752 (MR3) in rat kidney. Receptor activation in vitro was dependent upon the buffer, progressed just as well in the presence of the agonist and the antagonist, and was inhibited by molybdate. These necessitate a reassessment of both the importance of receptor activation in vitro and its possible contribution to hormone action in vivo.

Activation of cytosol aldosterone receptors in rat kidney

Cytosolic aldosterone-protein complexes are isolated from rat kidney slices after incubation with [3H]aldosterone and dexamethasone. Activated and unactivated forms of the complex are characterized by gel electrophoresis and hydroxyapatite chromatography after incubation at 4 degrees C and 25 degrees C respectively. It is found that the activated form reaches a maximum after 30 min at 25 degrees C and can be separated as an homogeneous peak by electrophoresis. Intermediate forms can also be identified. In the presence of 10 mM ATP, activation immediately occurs at 4 degrees C and is almost complete. In the presence of 10 mM molybdate, the activation is strongly enhanced and the increase in activated form may be about fifteen-fold whether molybdate is added during kidney homogenization or just before incubation at 25 degrees C. On the other hand molybdate reduces to one third the binding of the aldosterone-receptor complexes to nuclei. In the presence of the steroid RU 26988 which is a pure glucocorticoid, experiments done on aldosterone-receptors complexes and their binding to nuclei are confirmed. This proves that aldosterone is specific for mineralocorticoid sites. The general pattern of the mineralocorticoid receptor activation is discussed and its resemblance to the case of other steroid hormones is emphasized.

Induction of cleft palates: effects of triamcinolone acetonide on transcription in isolated nuclei

The effect of triamcinolone acetonide on the transcriptional activity in nuclei isolated from maternal A/J mouse livers and embryonic maxillary processes (EMP) has been studied. Triamcinolone acetonide (TAC, 13 mg/kg body weight) was administered to A/J mice on day 12.5 of gestation, and the mice were sacrificed at different time periods following injection. We find a significant increase in transcription in liver nuclei, and a decrease in this activity in nuclei from embryonic maxillary processes in response to TAC at 16 to 20 hours following injection. With the drug alpha-amanitin we show that the effect of TAC on transcription in EMP cannot be due to fluctuations in the concentration of endogenous RNA polymerase B. This is further substantiated by studies on the transcription of EMP-nuclei in the presence of exogenous DNA template. Relative to controls, the data demonstrates that the concentrations of RNA polymerases A and B in EMP-nuclei remain unchanged in response to TAC. Conversely, stimulated liver nuclei result in significant increases in the concentrations of RNA polymerases A and B. We therefore propose that in embryonic maxillary processes TAC induces changes in the chromatin template which may interfere with normal development.

Heterogeneity of steroid hormone receptor in adult rat lung cytosol

Chromatography on cellulose DEAE-52 columns revealed that the glucocorticoid receptor for rat lung cytosol consisted of a component in the 0.001 M prewash, revealed with synthetic steroids and natural mineralocorticoids, a second component eluted with 0.04 M PO4, labelled with triamcinolone, dexamethasone, and a third moiety in the 0.06 M PO4 region, evident with natural glucocorticoids (corticosterone, cortisol) as well as mineralocorticoids (aldosterone, deoxycorticosterone). The third component coeluted with rat blood serum transcortin in double labelled experiments. Rate lung was devoid of another component in the 0.02 M PO4 found in rat liver supernate and of the mineralocorticoid receptor evident only in rat kidney. Chromatography on Sephadex G-200 columns revealed a shift of radioactivity from a higher to a lower molecular weight region in the presence of 0.4 M KCl. Collectively, these studies indicate the subunit nature of the lung receptor as evidenced in most tissues hitherto tested. Moreover, polymorphism within a given subunit component can not be revealed by competition alone, as attempted by others, but can be revealed under selected conditions of physical separation.