ATP-Dependent Potassium Channels in the Kidney

The application of the patch-clamp technique (NEHER and SAKMANN 1976) to the kidney has led to the discovery of well-defined potassium (K) channels in the apical and basolateral membrane of tubule cells along the nephron. Such studies have permitted the biophysical characterization of renal K channels and defined several factors modulating their activity. A subfamily of these channels is distinguished by their sensitivity to alterations in metabolism including changes in cell pH, the level of hormones and cell messengers and ATP. These K channels play an important role in several transport processes in the proximal tubule, the thick ascending limb (TAL) of Henle’s loop, and in principal cells of the cortical collecting duct (CCD). ATP-sensitive channels are inhibited by an increase in the concentration of ATP in the cytosol of tubule cells, and such channel block can be relieved by ADP. ATP-sensitive channels have also been detected in several extrarenal tissues including brain, smooth, skeletal and heart muscle and s-cells of pancreatic islands (WANG W and HEBERT 1999). The molecular structure of one ATP-sensitive K channel has been defined by expression cloning (Ho et al. 1993) and disturbances of its function shown to play a key role in the inherited electrolyte disorder of Bartters’s syndrome (BARTER et al. 1962).