Intra-adrenal 11 beta-hydroxysteroid dehydrogenase plays a role in the regulation of corticosteroid secretion: An in vitro study in the rat

The expression of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) has been demonstrated in the adrenal glands, but until now little attention has been paid on its possible physiologic action. In-situ perfused rat adrenals released under basal conditions, in addition to mineralo- and glucocorticoids, notable amounts of 11-dehydrocorticosterone (DH-B), the inactive form to which corticosterone (the main glucocorticoid in rodents) is converted by 11 beta-HSD. The addition to the perfusion medium of glycyrrhetinic acid, a specific inhibitor of 11 beta-HSD, strongly reduced DH-B release and simultaneously evoked a moderate rise in both mineralo- and glucocorticoid output. The bolus administration of ACTH strikingly enhanced mineralo- and glucocorticoid secretion, but it significantly depressed DH-B release Rat adrenal microsome preparations possessed 11 beta-HSD activity, that was inhibited by glycyrrhetinic acid. Conversely, ACTH was without any apparent effect, a finding indicating that the in vivo observed ACTH-induced inhibition of adrenal 11 beta-HSD activity is mediated by an indirect mechanism whose elucidation requires further investigation. In conclusion, our present findings suggest that adrenal 11 beta-HSD plays a role in the regulation of steroid secretion in rats under both basal and stimulated conditions.