title: Characterization of a glucocorticoid receptor in the brains of chinook salmon, Oncorhynchus tshawytscha.
abstract: The effects of chronic stress on the brains of salmon may have important implications in light of the extremely high glucocorticoid levels experienced by migrating and spawning adults. The identification and the characterization of glucocorticoid receptors in salmon brains are the first steps in elucidating the effects of stress and high glucocorticoid levels on the brain. We have identified high-affinity, low capacity glucocorticoid receptors in chinook salmon (Oncorhynchus tshawytscha) brain cytosol and report the binding characteristics for the synthetic glucocorticoid triamcinolone acetonide (TA) and the naturally occurring salmonid glucocorticoid, cortisol. The binding characteristics for TA (Kd = 0.85 +/- 0.13 nM, B(max) = 22.4 +/- 2.97 fmol/mg protein, n = 7) and cortisol (Kd = 4.54 +/- 0.06 nM, B(max) = 25.40 +/- 2.20 fmol/mg protein, n = 2) demonstrated high-affinity, low capacity, and specificity for glucocorticoids. In competitive binding assays, TA, cortisol, and dexamethasone (a synthetic glucocorticoid) displaced [3H]TA most effectively, followed by RU38486. Corticosterone and RU28362 were weaker competitors. Cortisone was not a strong competitor nor were the sex steroids. Specific DNA binding was detected in DNA-cellulose chromatography assays. Receptors in nuclear extracts were not detected. These binding characteristics are consistent with published data on glucocorticoid receptors in other salmonid tissues.
authors.affiliation: Department of Fisheries and Wildlife, National Biological Service (CBS), Oregon State University, Corvallis 97331, USA.
authors.forename: I
authors.initials: I
authors.lastname: Knoebl
authors.forename: M S
authors.initials: MS
authors.lastname: Fitzpatrick
authors.forename: C B
authors.initials: CB
authors.lastname: Schreck
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D001921:Brain / Q000166:cytology / Q000648:ultrastructure; D001923:Brain Chemistry / Q000502:physiology*; D002845:Chromatography; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000302:isolation & purification; D005938:Glucocorticoids / Q000378:metabolism; D006854:Hydrocortisone / Q000097:blood; D007202:Indicators and Reagents; D007700:Kinetics; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D011965:Receptors, Glucocorticoid / Q000096:biosynthesis / Q000187:drug effects / Q000378:metabolism*; D012474:Salmon / Q000378:metabolism*; D014222:Triamcinolone Acetonide / Q000378:metabolism
chemical_list: D005938:Glucocorticoids; D007202:Indicators and Reagents; D009419:Nerve Tissue Proteins; D011965:Receptors, Glucocorticoid; D004247:DNA; D014222:Triamcinolone Acetonide; D006854:Hydrocortisone