Author:
Chakraborti P. K.,Weisbart M.
Abstract
In vitro binding of [3H]cortisol to brook trout liver cytosol and salt-soluble nuclear extracts demonstrated a high affinity (cytosol association constant, Ka = (0.18 ± 0.03) × 109M−1, n = 4; nuclear extract association constant, Ka = (0.033 ± 0.01) × 109M−1, n = 4) and low maximum binding capacity (cytosol, Nmax = 167 ± 18 fmol∙mg−1 protein, n = 4; nuclear extract, Nmax = 858 ± 81 fmol∙mg−1 protein, n = 4). Kinetics of binding of [3H]cortisol to cytosol at 2 °C revealed association and dissociation rate constants of 6.95 × 104∙M−1∙s−1 and 2.38 × 10−4 s−1, respectively. Gel filtration chromatography using Sephacryl S-300 as the matrix showed a molecular mass for the cytosol binding activity of 319 000 ± 4486 Da and Stokes' radius of 6.23 ± 0.03 nm (n = 3). Competition studies with different steroids indicated considerable specificity for the cytosol binding. The competitive hierarchy was as follows: dexamethasone > triamcinolone acetonide > Cortisol > corticosterone > cortisone > testosterone > estrone > 17β-estradiol > 11-deoxycortisol > progesterone > 11β, 17α, 21-trihydroxy-4-pregnen-3,20-dione-21-phosphate > 17α,20β-dihydroxy-4-pregnen-3-one > pregnenolone. These results support the concept of cytosolic and nuclear forms of glucocorticoid receptors in the liver of brook trout.
Publisher
Canadian Science Publishing
Subject
Animal Science and Zoology,Ecology, Evolution, Behavior and Systematics
Cited by
23 articles.
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