Potassium secretion and the regulation of distal nephron K channels.

K-selective channels in the luminal membranes of distal nephron segments form a key pathway for the secretion of K ions into the urine. This process is important to the control of K balance, particularly under conditions of normal or high K intake. This brief review will cover three issues: 1) the identification of apical K channels, 2) the role of these channels in the maintenance of K homeostasis, and 3) the role of aldosterone in this regulatory process. The large amount of literature on renal K transport has been elegantly summarized in a recent review in this journal [G. Giebisch. Am. J. Physiol. 274 (Renal Physiol. 43): F817-F833, 1998]. Here I will focus on a few prominent unsolved problems.