[Potassium channels and the kidney]

Potassium channels play an important role in several renal functions. These include the generation of a cell negative potential in all kidney cells, and potassium channels also participate importantly in the function of the thick ascending limb of Henle's loop and in principal tubule cells of collecting ducts. In the thick ascending limb (TAL), potassium channels mediate recycling of potassium ions across the apical membrane, thereby modulating the turnover of the Na/K/2Cl cotransporter. In the principal tubule cell, potassium channels play a key role in the secretion of potassium. The K channels in both the TAL and cortical collecting duct (CCD) have been cloned, and their functional properties are similar. Hereditary abnormalities of these K channels have been shown to lead to salt loss. Moreover, the delivery of sodium can be shown to be a key determinant of potassium secretion in the terminal nephron segment.