Effect of ACTH on the interconversion of ester and free cholesterol and corticosterone biosynthesis in rat adrenal glands.

After the administration of 3Hand 14C-cholesterol to rats 3 days and 4 hr prior to their death respectively, ester and free cholesterol in adrenal glands were successfully labeled separately with different isotopes. Examination of the 3H/14C ratio in free and ester cholesterol of adrenal glands and in plasma corticosterone enabled us to study of the role of ester cholesterol in corticosteroidogenesis in ACTH stimulated adrenal glands. By the ACTH administration, the rate of ester cholesterol hydrolysis was increased, while the rate of esterification of free cholesterol was decreased and the hydrolized cholesterol was incorporated into the free cholesterol pool in mitochondria, and then utilized for corticosterone biosynthesis. The administration of cycloheximide did not interfere with the stimulated rate of ester cholesterol hydrolysis in the ACTH-treated adrenals but it prevented the response of plasma corticosterone to ACTH.