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Characterization and Quantification of the Androgen and Glucocorticoid Receptors in Cytosol from Rat Skeletal Muscle

Characterization and Quantification of the Androgen and Glucocorticoid Receptors in Cytosol from... The binding of the radioactive synthetic hormonal steroids [3H]dexamethasone (9α‐fluoro‐11β, 17α, 21‐trihydroxy‐16α‐methyl‐1, 4‐pregnadiene‐3,20‐dione) and [3H]methyltrienolone (17β‐hydroxy17‐α‐methyl‐4,9,11‐estratrien‐3‐one) to cytosol from rat skeletal muscle was studied using dextrancoated charcoal to separate unbound and receptor‐bound steroid. The rates of association, dissociation, and degradation of the complexes of dexamethasone and methyltrienolone with receptor were highly dependent on temperature. The temperature dependence of association was greater for dexamethasone, and that of degradation was greater for methyltrienolone. Dissociation rates were insignificant for both steroid‐receptor complexes compared to association and degradation rates. The apparent equilibrium dissociation constants for the binding of dexamethasone and methyltrienolone to their receptor binding sites were about 7 and 0.3 nM, respectively, regardless of temperature (0, 15 or 23° C). The lack of influence of temperature on the equilibrium constants indicate that the binding was of hydrophobic character, and the corresponding free energy changes upon binding of dexamethasone and methyltrienolone to their respective binding sites were –41 and –49 kJ mol‐1 under equilibrium conditions at 0° C. The apparent maximum number of binding sites determined from Scatchard plots under these conditions was about 1900 fmol/g of tissue, 3500 fmol/mg of DNA or 30 fmol/mg of protein in the case of the dexamethasone receptor, and the corresponding figures for the methyltrienolone were about 100 fmol/g of tissue, 200 fmol/mg of DNA or 2 fmol/mg of protein. The ligand specificities of the binding sites for dexamethasone and methyltrienolone were typical of a glucocorticoid and an androgen receptor, respectively. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Febs Journal Wiley

Characterization and Quantification of the Androgen and Glucocorticoid Receptors in Cytosol from Rat Skeletal Muscle

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References (46)

Publisher
Wiley
Copyright
Copyright © 1980 Wiley Subscription Services, Inc., A Wiley Company
ISSN
1742-464X
eISSN
1742-4658
DOI
10.1111/j.1432-1033.1980.tb04977.x
Publisher site
See Article on Publisher Site

Abstract

The binding of the radioactive synthetic hormonal steroids [3H]dexamethasone (9α‐fluoro‐11β, 17α, 21‐trihydroxy‐16α‐methyl‐1, 4‐pregnadiene‐3,20‐dione) and [3H]methyltrienolone (17β‐hydroxy17‐α‐methyl‐4,9,11‐estratrien‐3‐one) to cytosol from rat skeletal muscle was studied using dextrancoated charcoal to separate unbound and receptor‐bound steroid. The rates of association, dissociation, and degradation of the complexes of dexamethasone and methyltrienolone with receptor were highly dependent on temperature. The temperature dependence of association was greater for dexamethasone, and that of degradation was greater for methyltrienolone. Dissociation rates were insignificant for both steroid‐receptor complexes compared to association and degradation rates. The apparent equilibrium dissociation constants for the binding of dexamethasone and methyltrienolone to their receptor binding sites were about 7 and 0.3 nM, respectively, regardless of temperature (0, 15 or 23° C). The lack of influence of temperature on the equilibrium constants indicate that the binding was of hydrophobic character, and the corresponding free energy changes upon binding of dexamethasone and methyltrienolone to their respective binding sites were –41 and –49 kJ mol‐1 under equilibrium conditions at 0° C. The apparent maximum number of binding sites determined from Scatchard plots under these conditions was about 1900 fmol/g of tissue, 3500 fmol/mg of DNA or 30 fmol/mg of protein in the case of the dexamethasone receptor, and the corresponding figures for the methyltrienolone were about 100 fmol/g of tissue, 200 fmol/mg of DNA or 2 fmol/mg of protein. The ligand specificities of the binding sites for dexamethasone and methyltrienolone were typical of a glucocorticoid and an androgen receptor, respectively.

Journal

The Febs Journal – Wiley

Published: Oct 1, 1980

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