THE RELATIVE POTENCY OF ADRENAL CORTICOIDS BY THE THYMUS INVOLUTION METHOD

Abstract

An adrenal corticoid which has an α-ketolic grouping at C17, a ketone or β-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-oxycorticosteroid is increased approximately 3 to 3.5 times by the addition of an α-hydroxyl at C17. The ability of a 17-hydroxycorticosteroid to cause thymic atrophy is enhanced 1.2 times by acetylation at C21, 1.5 times by replacement of a ketone at C11 with β-hydroxyl group, 4 to 5 times by the formation of a 1,2 double bond, and 8 to 10 times by the introduction of a fluorine atom in the α position at C9. The potency of Δ1-11-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. The relative activities of adrenal corticoids as determined by the thymus involution method do not differ significantly from those obtained by other glucocorticoid bio-assays.