title: Affinity-labeling steroids as biologically active probes of antiglucocorticoid hormone action.
abstract: The role of the glucocorticoid receptor in the expression of antiglucocorticoid action has been investigated with a chemically-reactive derivative of three glucocorticoid steroids with differing biological potencies, i.e. the C-21 mesylates of cortisol, dexamethasone and deacylcortivazol. Dexamethasone 21-mesylate (Dex-Mes) was the most useful derivative due to its favorable balance of high receptor affinity and predominantly irreversible antiglucocorticoid activity. A number of criteria have been used to conclude that [3H]Dex-Mes covalently labels glucocorticoid receptors in the steroid-binding cavity. The available data indicate that covalent Dex-Mes-labeled receptors (mol. wt approximately equal to 98,000) are responsible for the irreversible antiglucocorticoid activity while the partial agonist activity of Dex-Mes is due to non-covalent Dex-Mes-bound receptors. Further support for this hypothesis comes from the observations that deacylcortivazol 21-mesylate was a full glucocorticoid and did not affinity label receptors (and marginally labeled cytosol proteins) although it was capable of covalently-labeling bovine serum albumin. Several mechanisms for the expression of irreversible antiglucocorticoid activity by covalent Dex-Mes-labeled receptors were examined and can be eliminated. Covalent receptor-Dex-Mes complexes formed in whole HTC cells were found to have a decreased capacity for nuclear binding. This decreased nuclear-binding capacity could be responsible for the whole-cell irreversible antiglucocorticoid activity of Dex-Mes.
mesh_terms: D000345:Affinity Labels; D000818:Animals; D002478:Cells, Cultured; D003907:Dexamethasone / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D005938:Glucocorticoids / Q000037:antagonists & inhibitors*; D006854:Hydrocortisone / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D011281:Pregnatrienes / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D014316:Tritium
chemical_list: D000345:Affinity Labels; D005938:Glucocorticoids; D011281:Pregnatrienes; D011965:Receptors, Glucocorticoid; D014316:Tritium; C041705:deacylcortivazol 21-mesylate; C027504:cortisol 21-mesylate; D003907:Dexamethasone; C031710:dexamethasone 21-methanesulfonate; D006854:Hydrocortisone