Hormonal Regulation of the Epithelial Sodium Channel ENaC : N or P_o?

Despite large changes in water and salt intake, the kidney is able to maintain the extracellular osmolarity and volume within narrow margins (Verrey et al., 2000). Such fine control requires specific factors or hormones; among them, aldosterone and antidiuretic hormone (ADH) (vasopressin in mammals) play the key role. The main effector for the sodium balance is the epithelial sodium channel expressed in the apical membrane of the principal cell located in the distal nephron (distal convoluted tubule and collecting duct). The effect of aldosterone on sodium transport has been highly conserved throughout the evolution of vertebrates, whereas that of vasopressin varies from species to species. In the urinary bladder of the toad (Girardet et al., 1986) and in the cortical collecting duct (CCD) of the rat (Reif et al., 1986), ADH increases sodium transport through a cAMP-dependent mechanism, via...