Abstract
In an attempt to delineate the effect of corticotropin (ACTH) on post-pregnenolone steroidogenesis, the activity of enzymatic systems operative in conversion of pregnenolone into glucocorticoids and androgens was studied in adrenocortical cells from control rabbits and from animals treated with ACTH for 12 days (ACTH 1–24, 200 μg s.c. daily). The cells from ACTH-treated rabbits exhibited an increased overall steroidogenic capacity and produced much more cortisol ( P < 0.0005) as well as other 17-hydroxylated steroids as a result of increased activity of 17α-hydroxylase; corticosterone generation was concomitantly reduced. The increased conversion of pregnenolone or progesterone into androgens, as a result of previous treatment with ACTH, provides additional evidence for an effect of ACTH on 17α-hydroxylase activity. A stimulatory effect of ACTH on 11β-hydroxylase was also evidenced by these cells, since conversion of 11-deoxycortisol into cortisol was enhanced ( P < 0.005). The increased production of androgens from 17-hydroxylated precursors by cells from ACTH-treated rabbits suggests that ACTH also exerts a prolonged stimulatory effect on 17,20-lyase. The activity of 3β-hydroxysteroid dehydrogenase-isomerase was apparently not influenced by chronic treatment with ACTH, judged from unchanged conversion of dehydroepiandrosterone into androstenedione. The activity of 11β-dehydrogenase was likewise unchanged in these conditions.
Published Version
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