title: Evidence that pH induced activation of the rat hepatic glucocorticoid-receptor complex is irreversible.
abstract: The possible reversibility of pH induced activation of the glucocorticoid-receptor complex was studied. Generally, this was accomplished by activating rat liver cytosol at pH 8.5 (15 degrees C, 30 min), and then returning it to pH 6.5 for a second incubation (15 degrees C, 30 min). Activation was quantitated by measuring the binding of [3H]triamcinolone acetonide [( 3H]TA)-receptor complexes to DNA-cellulose. When cytosol was incubated at pH 6.5, only 4.1% of the [3H]TA-receptor complexes bound to DNA-cellulose. However, 39.2% of the complexes bound when the cytosol was pH activated. When pH activation was followed by a second incubation at pH 6.5, 47.0% of the steroid-receptor complexes bound. Thus, according to the DNA-cellulose binding assay, pH induced activation was irreversible. In order to visualize both activated and unactivated [3H]TA-receptor complexes during this process, diethylaminoethyl (DEAE)-cellulose chromatography was performed. When cytosol was incubated at pH 6.5, only 19.6% of the [3H]TA-receptor complexes were eluted in the activated form from DEAE-cellulose. However, 67.5% of the complexes were eluted in the activated form when cytosol was pH activated. When pH activation was followed by a second incubation at pH 6.5, 74.9% of the steroid-receptor complexes were eluted in the activated form. Thus, DEAE-cellulose chromatography also showed that pH induced activation was irreversible. This is the first known report that the combination of DNA-cellulose binding and DEAE-cellulose chromatography have been used to study pH induced activation of the glucocorticoid-receptor complex. By these criteria, we conclude that in vitro pH induced activation is irreversible.
mesh_terms: D000315:Adrenalectomy; D000818:Animals; D002482:Cellulose / Q000031:analogs & derivatives; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000031:analogs & derivatives; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000302:isolation & purification / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism*; D014222:Triamcinolone Acetonide / Q000378:metabolism
chemical_list: C033190:DNA-cellulose; D011965:Receptors, Glucocorticoid; D011987:Receptors, Steroid; D002482:Cellulose; D004247:DNA; D014222:Triamcinolone Acetonide