Expression cloning of the epithelial sodium channel

Complex organisms take sodium from the external environment to achieve and maintain extracellular volume and blood pressure. Many sodium transporter systems have evolved, and among them the epithelial sodium channel plays a fundamental role in determining the final amount of sodium reabsorbed. Epithelial sodium channels are present in the apical membrane of cells lining the distal segment of the nephron, urinary bladder, distal colon, and the airways. In the skin they are found in the sweat ducts and in certain animals (amphibians) they are also present in the epidermal cells. All these tissues absorb sodium via an amiloride-sensitive, highly selective Na + channel. This paper discusses recent efforts that have lead to the cloning and the elucidation of the structure of the epithelial sodium channel.