Abstract 277: Mutations in the KCNJ5 Gene Imply a Higher Lateralization Index at Adrenal Vein Sampling for Primary Aldosteronism
Background. The mutations that affect the selectivity filter of the KCNJ5 K+ channel can play a role in triggering and/or maintaining aldosterone oversecretion in primary aldosteronism (PA). We therefore hypothesized that these somatic mutations can be associated with an increased aldosterone secretion from the APA, thus translating in raised plasma aldosterone concentrations (PAC) in the ipsilateral adrenal vein.
Aim. To investigate if the lateralization index (LI) at adrenal vein sampling (AVS) is higher in the patients with an APA carrying the mutation (KCNJ5mut), as compared to those without the mutation (KCNJ5wt).
Methods. Ninety-two consecutive PA patients who underwent AVS and received diagnosis of APA based on the four corners criteria were recruited. Unequivocal information on the presence or absence of the KCNJ5 mutations was available for each patient. The selectivity index (SI) was calculated as ratio between the right or left adrenal vein PCC (PCCside) and the infrarenal IVC PCC and a cutoff of 2.00 was used. The lateralization index (LI) was calculated in the bilaterally selective AVS as the ratio of PAC/PCC at the APA side to PAC/PCC at the contralateral side. We sequenced the KCNJ5 coding region spanning aminoacids 122 to 199, which include the selectivity filer.
Results. The overall prevalence rate of KCNJ5 somatic mutations was 34%; G151R, L168R and T158A mutations were found in 19, 10 and 1 APA respectively. The G151E mutation was not found. The KCNJ5mut and KCNJ5wt groups were similar for gender, age, sK+ levels, while PAC and ARR were higher, and PRA lower (all p<0.05) in the KCNJ5 mut group. In the latter group the LI was higher than in the KCNJ5wt group (29.3± 6.7 vs 16.7±3.9, p< 0.02). This was due to a PAC/PCC ratio which was higher in the adrenal vein ipsilateral to the APA side and lower contralaterally in the KCNJ5mut group.
Conclusions. These results provide direct in vivo evidence for a higher aldosterone secretion from APA carrying the KCNJ5 mutations, which translates into higher values of the LI, compared to the tumors without such mutations. Hence, the presence of these KCNJ5 mutations can affect the accuracy of the AVS-based diagnosis of the subtype of PA.
- © 2012 by American Heart Association, Inc.