Inhibition of Adrenal Protein Synthesis by Steroidsin Vitro1

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Abstract
The effect of certain steroids upon rat adrenal protein synthesis in vitro was evaluated by measuring the incorporation of 14C-leucine into protein. The addition of 5.6 x 10-4 [image] corticosterone to the incubation media inhibited protein synthesis by 91%. A dose related inhibition has been shown. Progesterone and ACTH, both of which enhance corticosterone formation, inhibited protein synthesis by 64 and 19%, respectively; cortisol inhibited it by 44%. Cholesterol and aldosterone had no effect. In order to study the effect of inhibition of protein synthesis on cortlcosterone production, studies with testosterone, a nonprecursor for corticosterone, carried out. Testosterone 6.9 x 1014 [image] markedly inhibited protein synthesis in the adrenal (93%), and the inhibition was as great as that reported with 1 x 10-3 [image] puromycin. Like puromycin, testosterone blocked the stimulation of corticosterone by ACTH. This in vitro effect of testosterone is consistent with the reports of its inhibition of the steroidogenic effect of ACTH in vivo. These data suggest that certain steroids may inhibit adrenal steroid production and this effect may be mediated by the inhibition of adrenal protein synthesis. It is consistent with the hypothesis of a local feecback inhibition of steroidogenesis by adrenal steroids.