Relative affinity of 17α- and/or 21-esters and 17α,21-diesters of cortisol for a glucocorticoid receptor from rat thymocytes

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Abstract
The affinity, relative to cortisol, of 17.alpha.- and 21-esters and 17.alpha.,21-diesters of cortisol for the glucocorticoid receptor of rat thymus cytosol was determined by a competitive binding assay which used [3H]dexamethasone. Esterification of the 21-hydroxy group of cortisol caused a loss of relative affinity to 0.046 for acetate and 0.32 for valerate. Esterification of the 17.alpha.-hydroxy group resulted in an increase in relative affinity to 1.14 for acetate, 12.4 for butyrate, and 11.5 for valerate. Diesters had relative affinities which reflected both trends. Thus, the 21-acetate, 21-propionate, 21-butyrate, and 21-valerate of cortisol 17-acetate had relative affinities of 0.036, 0.093, 0.152 and 0.272. The 21-acetate, 21-propionate and 21-butyrate of cortisol 17-valerate had relative affinities of 0.76, 1.17 and 1.33.