Small Potassium Channels
Speculation on a Role to Regulate Aldosterone Production and Blood Pressure
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See related article, pp 785–795
In the current issue of Hypertension, Yang et al1 report on the presence of small conductance, calcium (Ca++)–activated potassium (K+) channels (SK channels) in a human adrenocortical cell line (H295R). SK channels were also found in normal human adrenals. Using pharmacological probes, these investigators showed relevance to synthesis of aldosterone: a specific SK channel inhibitor, apamin, increased expression of steroidogenic enzymes and increased both basal and angiotensin II–stimulated aldosterone production. 1-ethyl-benzimidazolinone (1-EBIO), an agonist of SK channels, produced opposite effects. The authors suggest that a dysfunctional SK channel could decrease a restraining influence on secretion of aldosterone. Some degree of caution should be applied to the findings. There was a heavy reliance on nonbiological probes and the use of a human cell line (NIH-H295). Although a widely used source of adrenocortical cells, any cell line can lose certain functions over time. Replication by other laboratories will be important.
Produced in the adrenal zona glomerulosa, aldosterone is a potent sodium (Na+)–retaining, K+-secreting hormone. Angiotensin II and K+ stimulate its production to, respectively, maintain plasma volume and prevent hyperkalemia.2 Both stimuli act by first decreasing a highly polarized …