The amiloride-sensitive epithelial sodium channel (ENaC) is essential in regulating transepithelial transport of sodium in electrically tight epithelia, such as the renal collecting duct, the surface epithelium of the distal colon, the ducts of salivary and sweat glands, and airway cells (Duc et al., 1994; Farman et al., 1997). Its location in the apical membrane, facing the tubular fluid, drives sodium entry into the cell. Sodium is then extruded from the cell at the basolateral membrane by the Na+-K+-ATPase. Coordinate activities of apical sodium channels and the basolateral sodium pump allow efficient transcellular sodium transport without affecting cell sodium concentration. ENaC expression has also been found in epithelia like the skin where the channel seems implicated in differentiation processes (Mauro et al., 2002). Three subunits (α, β and γENaC) have been characterized encoded by different genes on human chromosomes 12 (SCNN1A) and 16 (SCNN1C, SCNN1B). In mouse, the genes have been localized on chromosomes 6 (Scnn1a) and 7