Na+/H+ exchanger subtypes in the renal tubule: function and regulation in physiology and disease.

Four members of the Na+/H+ (NHE) exchange family are present in the renal tubule. NHE1, ubiquitously expressed, amiloride-sensitive and growth factor-activatable, is present in the basolateral membrane of most segments of the renal tubule. NHE2 and NHE3 are present in the apical membrane of renal tubule segments, except the collecting duct. NHE4 is probably a basolateral isoform. NHEs are involved in multiple functions, cell pH and volume regulation, and transepithelial transport of NaCl, NaHCO3, and NH4+. The present review deals with the recent developments in the functions of NHEs, the effects of hormones, osmolality, acid base status, and potassium stores of Na+/H+ exchange at the cellular and molecular levels. Finally, the alterations of NHE activities in some renal disease processes are briefly discussed.