Abstract 279: Involvement of Kcnj5 Mutations on Excessive Aldosterone Sythesis When Incubated With Acth by Cells Isolated From Aldosterone-producing Adenoma.
Objective: Our objective was to investigate the steroidogenic activity by in vitro incubating adrenocortical cells, isolated from aldosterone- producing adenomas (APA) tissues with/without mutations of the KCNJ5 gene in order to clarify the mechanisms of autonomous production of aldosterone in patients with primary aldosteronism (PA).
Design and Patients: We subjected 22 cases with APA and sequenced KCNJ5 cDNA by using resected tissues of APA. We divided them to 16 APAs with mutations of the KCNJ5 gene (mutated group) and 6 APAs without its mutations (wild type group). Isolated cells were prepared soon after removing APA tissues, and the cells were incubated with various stimulants, including ACTH and Bt2cAMP. The mRNA expression of each steroidogenic enzyme was also determined by RT-PCR.
Results: Responsiveness of aldosterone production (A-P) by isolated cells to ACTH and Bt2cAMP was greater in the mutated group than in the wild type group, although basal amount of A-P incubated for 2hrs without any stimulants was equal between two groups. Responsiveness of A-P to TPA and TPA+ Ca ionophore was greater in the mutated group than in the wild type group. Tissue extracts of mRNA without any stimulations revealed that the mutated group demonstrated higher expression of 17-hydroxylase/3HSD2 than the wild type group, which showed greater expression of CYP11B2 than the mutated group.
Conclusion: In vitro incubation studies demonstrated that ACTH might play a crucial role on up-regulating autonomous production of A-P in APA tissues with mutations of the KCNJ5 gene, although the basal expression of CYP11B2 was lower in the mutated group. Moreover, the mutated group showed high ratio of the basal expression of 17-hydroxylase/3HSD2, suggesting that the mutated group can produce cortisol rather than aldoterone via supplying 17-hydroxylated substrates at the static condition, while cAMP-dependent systems or C-kinase-dependent systems activated by ACTH seem to strongly promote activation of A-P steps in the mutated group, rather than in the wild type group.
- © 2012 by American Heart Association, Inc.