title: Some aspects of dexamethasone binding in the old rat liver.
abstract: The maximal glucocorticoid responsiveness and the adaptation degree are reduced in old rat liver as demonstrated by cortisol stimulation of RNA polymerases. Nevertheless the concentration of unoccupied 3H-dexamethasone binding sites in molybdate-stabilized cytosol of adrenalectomized old animals is significantly increased in comparison with young adult rats. The KD constants showed an increasing tendency, but not a significant one. In the molybdate-free cytosol the results are similar. First studies of the binding kinetics in the molybdate-free system showed a sigmoidal saturation curve in the cytosol of young adult rats, but usual hyperbolic saturation kinetics in the cytosol of old animals. The Hill coefficient was 1.0 +/- 0.1 for old and 1.9 +/- 0.3 for young animals. The binding of activated 3H-dexamethasone receptor complexes to liver nuclei showed no significant age-dependent differences in binding kinetics, acceptor site concentration or affinity. Attention must be paid to altered glucocorticoid receptor binding in the cytosol and in nuclei as a potential cause of changes in hormone-induced gene expression at the pretranscriptional level.
authors.affiliation: Institute of Clinical Chemistry, Karl Marx University Leipzig, GDR.
authors.forename: H
authors.initials: H
authors.lastname: Martin
authors.forename: R
authors.initials: R
authors.lastname: Martin
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D003907:Dexamethasone; D005260:Female; D008099:Liver / Q000378:metabolism*; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000378:metabolism*
chemical_list: D011965:Receptors, Glucocorticoid; C028697:dexamethasone receptor; D003907:Dexamethasone