THE RELATIVE POTENCY OF ADRENAL CORTICOIDS BY THE THYMUS INVOLUTION METHOD

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Abstract
An adrenal corticoid which has an alpha-ketolic grouping at C17, a ketone or beta-hydroxyl at C11, a ketone at C3, and a double bond in the 4,5 position is able to involute the thymus gland of the weanling rat. The thymolytic activity of an 11-oxycorti-costeroid is increased approximately 3-3.5 times by the addition of an alpha-hydroxyl at C17. Ability of a 17-hydrocorticosteroid to cause thymic atrophy is enhanced 1.2 times by acetylation at C21, 1.5 times by replacement of a ketone at C11 with a beta-hydroxyl group, 4 to 5 times by the formation of a 1,2 double bond, and 8-10 times by the introduction of a fluorine atom in the alpha position at C9. The potency of [DELTA]1-11-oxycorticosteroids relative to naturally occurring corticoids is significantly greater when the steroids are injected in an aqueous medium than when they are given in corn oil. Relative activities of adrenal corticoids as determined by the thymus involution method do not differ significantly from those obtained by other gluco-corticoid bio-assays.