Testosterone inhibits Human Wild-Type and Chimeric Aldosterone Synthase Activity In-vitro

We have recently reported that in vitro, the wild-type (ASWT) and chimeric aldosterone synthase (ASCE) enzymes are inhibited by progesterone and estradiol had no effect. To explore the direct action of testosterone on wild-type and chimeric aldosterone synthase enzymes, we carried out an in vitro assay using HEK-293 cells transiently transfected with vectors containing the full ASWT or ASWT cDNAs. The effect of testosterone on AS enzyme activities was evaluated incubating with deoxycorticosterone (DOC) with or without increasing doses of testosterone. Aldosterone production was measured by HPLC-MS/MS. Docking of testosterone within the active sites of both enzymes was performed. In this system, testosterone inhibited ASWT, (90% inhibition at 5 μM, IC50=1.690 μM) with higher efficacy and potency than the ASCE (80% inhibition at 5 μM, IC50=3.176 μM). Our results show an inhibitory effect of testosterone on aldosteronesynthesis by ASWT or ASCE enzyme. This effect is a novel regulatory mechanism of testosterone action, which could affect the screening and diagnosis of primary aldosteronism.