Context: Congenital adrenal hyperplasia (CAH) is caused by 21-hydroxylase deficiency in 95% of the cases. This leads to accumulation of steroid precursors prior to the enzymatic block and increased adrenal androgen production; accordingly serum concentrations of 17-hydroxyprogesterone (17OHP), androstenedione and testosterone are elevated in affected patients.
Objective: To analyse the effect of 17OHP, androstenedione and testosterone on aldosterone-mediated transactivation of the human mineralocorticoid receptor (hMR).
Methods: A transactivation assay, using the mammalian COS7 cells, was performed to evaluate the effect of 17OHP and androstenedione on MR transactivation driven by aldosterone. Cells were co-transfected with hMR-cDNA, MMTV-luc and renilla expression vectors. Transfected cells were incubated with six different steroid concentrations in addition to aldosterone (1010 M). After 24 hours of incubation luciferase and renilla activities were measured using a luminometer, as a measure of hMR transactivation (luciferase) and transfection efficiency (renilla), respectively. Results were analysed by both ANOVA with Bonferroni adjustment for multiple comparisons and linear regression analyses.
Results: 17OHP concentrations (5 nM1000 nM) significantly inhibited hMR transactivation by aldosterone. Linear regression analysis showed statistically significant linear inhibition of transactivation of the hMR by 1010 M aldosterone in the presence of increasing 17OHP concentrations (F(1, 5)=11.34, P=0.019). Neither androstenedione nor testosterone did affect hMR transactivation by 1010 M aldosterone.
Conclusion: Our study shows for the first time that neither androstenedione nor testosterone have an effect on the aldosterone-mediated transactivation of the hMR. 17-OHP has an anti-mineralocorticoid effect in vitro. Concentrations of sex steroids should be normalized to normal concentrations for age and sex. To reduce the anti-mineralocorticoid action of 17OHP in CAH patients, 17OHP values lowered to around 20 nmol/l might improve mineralocorticoid response.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.