TASK1 and TASK3 are two-pore domain potassium channels (K_2P) highly expressed in adrenal glands. Both channels are believed to contribute to the background conductance which is involved in the control of aldosterone secretion by angiotensin II and by high plasma potassium. Recently, we observed that TASK1-knockout mice exhibit a severe primary hyperaldosteronism paralleled by a sex- and age-dependent adrenocortical zonation defect. Here, we investigated the expression and localization of the K_2P channels TASK1, TASK2, and TASK3 in murine and in human adrenal glands. In mouse adrenal gland, in situ hybridization revealed expression of TASK1 in the zona glomerulosa and zona fasciculata and expression of TASK3 specifically in zona glomerulosa cells. TASK2 expressing cells of the inner adrenal cortex were labeled by TASK2 promotor-driven LacZ staining.

In human adrenal tissue, TASK1 expression pattern was similar to mouse adrenal glands with strongest signal in the zona glomerulosa and zona fasciculata. Using realtime PCR, the expression of K_2P channels and of steroidogenic pathway enzymes was measured in normal and adenoma tissue. Adenoma showed increased expression of TASK1, TREK1, and aldosterone synthase. These data for the first time show the localization of TASK1 in human adrenal glands and point to a possible involvement of K_2P-channels in the development, hormonal activity and/or progression of adrenal adenoma.