IN VIVO CONVERSION OF RADIOACTIVE PROGESTERONE AND CORTICOSTERONE TO ADRENAL CORTICAL HORMONES IN NORMAL AND ACTH-TREATED RATS

Abstract

ABSTRACT For the study of biosynthetic pathways and their alterations under various experimental conditions, the method of in vivo conversion is more suitable than in vitro incubation experiments. In rats, in vivo conversion of radioactive progesterone to corticosterone and aldosterone and of corticosterone to aldosterone was demonstrated. The conversion of progesterone and corticosterone to aldosterone occurred only in the presence of the adrenals, while a minimum extra-adrenal conversion of progesterone to corticosterone was observed. After the administration of ACTH for 9 to 25 days, the adrenals became hypertrophied, and an increased conversion rate from progesterone to corticosterone was demonstrated. Simultaneously, the conversion rate of corticosterone to aldosterone was decreased. Such a change in the biosynthetic pathway of aldosterone may at least in part be responsible for the reduced production of aldosterone from endogenous precursors, observed after repeated administration of ACTH.