Competitive binding studies with glucocorticoid receptors from rat-thymus cells: differential temperature-dependence of steroid binding. |
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Authors: | T R Jones J C Sloman P A Bell |
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Institution: | Tenovus Institute for Cancer Research, The Welsh National School of Medicine, The Heath, Cardiff CF4 4XX, Wales, Great Britain |
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Abstract: | Competitive steroid-binding studies were performed with intact rat thymus cells and with cytosol preparations at different temperatures using 1,2-3H]dexamethasone as the labelled ligand. Steroids lacking a 17 alpha-hydroxyl group, such as corticosterone, were better able to compete with 1,2-3H]dexamethasone for binding to glucocorticoid receptors at 0 degrees C than compounds containing a 17 alpha-hydroxyl substituent, such as cortisol. At 37 degrees C the reverse was true. This temperature-dependent change in relative affinities appeared to be unrelated to steroid metabolism or receptor activation, and to depend only on the thermodynamic parameters of the steroid--receptor interaction. Relative biological activities for different steroids agree more closely with the relative affinities determined at 37 degrees C than with those determined at lower temperatures. |
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Keywords: | rat thymus glucocorticoids receptors competition temperature effects dexamethasone 9α-fluoro-16α-methyl-1 1β 17 21-trihydroxypregna-1 4-diene-3 20-dione cortisol 11β 17 21-trihydroxypregn-4-ene-3 20-dione 21-deoxycortisol 11β 17-dihydroxypregn-4-ene-3 20-dione corticosterone 11β 21-dihydroxypregn-4-ene-3 20-dione cortexolone 17 21-dihydroxypregn-4-ene-3 20-dione 11β-hydroxyprogesterone 11β-hydroxypregn-4-ene-3 20-dione 17-hydroxyprogesterone 17-hydroxypregn-4-ene-3 20-dione deoxycorticosterone 21-hydroxypregn-4-ene-3 20-dione progesterone pregn-4-ene-3 20-dione |
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