11beta-hydroxysteroid dehydrogenase expression and activity in the human adrenal cortex

Prior research has shown that 11beta-hydroxysteroid dehydrogenase (11beta-HSD) plays a role in regulating glucocorticoid activity in peripheral tissues. However, the expression and activity of this enzyme in the human adrenal cortex remain poorly understood. Established knowledge indicates that 11beta-HSD2 is critical for mineralocorticoid receptor specificity by inactivating cortisol. This gap motivated the investigation into whether human adrenal tissue expresses and utilizes 11beta-HSD2. No prior work had resolved the functional role of 11beta-HSD2 in the adrenal cortex. Existing studies focused on peripheral tissues rather than the adrenal gland itself. This uncertainty drove the need for direct experimental assessment of 11beta-HSD2 in human adrenal samples. The lack of data on adrenal 11beta-HSD2 activity created a significant knowledge gap. Understanding this enzyme's role could clarify how glucocorticoid inactivation occurs within the adrenal gland. These findings could also inform broader research on steroid hormone regulation.

The study aimed to investigate the expression and activity of 11beta-HSD2 in the human adrenal cortex. Researchers sought to determine whether this enzyme is present and functional in human adrenal tissue. The specific problem addressed was the lack of data on 11beta-HSD2 in adrenal physiology. The motivation stemmed from the known role of 11beta-HSD2 in peripheral tissues and its potential relevance in the adrenal gland. The study also aimed to assess how 11beta-HSD2 activity is modulated by adrenal hormones and stress signals. The researchers focused on the conversion of cortisol and corticosterone to their inactive forms. They examined whether 11beta-HSD2 activity is influenced by adrenal stimulation or inhibitors. The goal was to clarify the enzyme's role in glucocorticoid inactivation within the adrenal cortex.

The researchers used human adrenal cortex tissue samples obtained from decapsulated adrenal slices. Microsomal preparations were made to assess 11beta-HSD2 activity. The enzyme's expression was confirmed through gene analysis of adrenal tissue. The study measured the secretion of cortisol, corticosterone, cortisone, and 11-dehydrocorticosterone from adrenal slices. Inhibitors like glycyrrhetinic acid were used to test the enzyme's function. The effects of ACTH and angiotensin II on hormone secretion were evaluated. Radioactive cortisol was used to track conversion to cortisone in adrenal slices. The study also tested the impact of aminoglutethimide and cyanoketone on enzyme activity.

The study found that human adrenal cortex expresses the 11beta-HSD2 gene and exhibits high 11beta-HSD2 activity. Adrenal slices secreted significant amounts of cortisone and 11-dehydrocorticosterone under basal conditions. Glycyrrhetinic acid increased cortisol and corticosterone production while reducing cortisone and 11-dehydrocorticosterone. ACTH and angiotensin II increased cortisol and corticosterone but decreased cortisone and 11-dehydrocorticosterone. ACTH also reduced the conversion of [3H]cortisol to [3H]cortisone in adrenal slices. Aminoglutethimide and cyanoketone reversed this effect of ACTH. Metyrapone did not affect the conversion process. These findings suggest that 11beta-HSD2 is actively involved in inactivating glucocorticoids in the adrenal cortex.

The authors concluded that the human adrenal cortex possesses active 11beta-HSD2, which inactivates newly formed glucocorticoids. The enzyme's activity is modulated by agonists of glucocorticoid secretion through an indirect mechanism. The suppression of cortisone and 11-dehydrocorticosterone by ACTH and angiotensin II suggests a regulatory role. The effect of ACTH on 11beta-HSD2 activity is likely mediated by steroid synthesis inhibitors. The study's findings support the presence of functional 11beta-HSD2 in the adrenal cortex. The enzyme's activity is negatively influenced by adrenal stimulation. The modulation of 11beta-HSD2 may involve changes in intra-adrenal steroid concentrations. These conclusions align with the observed effects of inhibitors on enzyme activity.