CHARACTERIZATION OF A GLUCOCORTICOID RECEPTOR IN THE BRAINS OF CHINOOK SALMON, ONCORHYNCHUS-TSHAWYTSCHA

The effects of chronic stress on the brains of salmon may have importa nt implications in light of the extremely high glucocorticoid levels e xperienced by migrating and spawning adults. The identification and th e characterization of glucocorticoid receptors in salmon brains are th e first steps in elucidating the effects of stress and high glucocorti coid levels on the brain. We have identified high-affinity, low capaci ty glucocorticoid receptors in chinook salmon (Oncorhynchus tshawytsch a) brain cytosol and report the binding characteristics for the synthe tic glucocorticoid triamcinolone acetonide (TA) and the naturally occu rring salmonid glucocorticoid, cortisol. The binding characteristics f or TA (K-d = 0.85 +/- 0.13 nM, B-max = 22.4 +/- 2.97 fmol/mg protein, n = 7) and cortisol (K-d = 4.54 +/- 0.06 nM, B-max = 25.40 +/- 2.20 fm ol/mg protein, n = 2) demonstrated high-affinity, low capacity, and sp ecificity for glucocorticoids. In competitive binding assays, TA, cort isol, and dexamethasone (a synthetic glucocorticoid) displaced [H-3]TA most effectively, followed by RU38486. Corticosterone and RU28362 wer e weaker competitors. Cortisone was not a strong competitor nor were t he sex steroids. Specific DNA binding was detected in DNA-cellulose ch romatography assays. Receptors in nuclear extracts were not detected. These binding characteristics are consistent with published data on gl ucocorticoid receptors in other salmonid tissues. (C) 1996 Academic Pr ess, Inc.