Aldosterone-regulated ion transporters in the kidney.

Madin-Darby canine kidney (MDCK) cells resemble intercalated cells of the renal collecting duct. In these cultured epithelial cells aldosterone activates apical Na+/H+ exchange, initiating a cascade of intracellular events such as cell growth, epithelial cell polarity, and stimulation of transepithelial ion transport. Transepithelial K+ secretion is triggered by the insertion of new ion channels and the activation of previously quiescent channels with increasing cytoplasmic pH. Aldosterone supplies the cell with ion transporters necessary for adequate function of the renal collecting duct when the organism is metabolically challenged.