THE RELATIVE THYMOLYTTC ACTIVITIES OF CORTICOIDS USING THE OVARIECTOMIZEDADRENALECTOMIZED MOUSE1

Abstract

The thymus gland of the adrenalectomized-ovariectomized mouse is a suitable test object for the bioassay of corticoids administered subcutaneously or orally. The response consisted of an inverse relationship between dose and thymus size. When a total of 44 to 56 mice were used on the standards plus unknowns (two concentrations of each), an index of precision (λ) of 0.221 (range 0.118 to 0.408) was found for the assay of cortisone and cortisol. Increasing doses of cortisol and cortisone and some related steroids produced increasing thymic involutions to 25% of the control size. Desoxycorticosterone produced statistically significant involutions, but the curve appears to level off at 75% of the initial thymus size. On this basis, desoxycorticosterone appears to give a qualitatively different response than that found for the cortisol and cortisonegroup of steroids. No true thymolytic effect could be demonstrated for the estrogens estradiol-1² and stilbestrol, but testosterone and progesterone produced significant but limited thymus involution at relatively high dosage levels. When the activity of cortisol, by the subcutaneous route, was assigned an activity of 100%, the following relative activities were found: 9±-fluorocortisol, 272% ± 11; cortisone, 79% ± 4.0; 9±-hydroxy cortisol, 57% ± 5.1; corticosterone, 45% ± 4.5; 21-desoxycortisol, 35% ± 2.5; and desoxycorticosteronc, 12% ± 0.6.