Characteristics and regulatory mechanisms of the amiloride-blockable Na+ channel

Studies of active Na+ transport across intact amphibian skin and bladder epithelia and, more recently, epithelial cells in culture have served as prototypes for understanding transport function in other experimentally less accessible epithelia such as renal tubules, lung, and sweat glands. Epithelia of diverse phylogenetic origin contain amiloride-blockable Na+ channels that are undoubtedly involved in the regulation of transepithelial Na+ transport and electrolyte homeostasis. With the advent of the techniques of tissue culture, patch clamp, isotope flux measurements in native vesicles and liposomes, and planar lipid bilayer reconstitution, it has now become possible for the first time to explore the functional operation and regulation of this widespread and important transport protein at the molecular level. Epithelial transport physiology has now reached a point where investigators can embark on studies concerning the cellular and molecular biology of epithelial Na+ channels. In our opinion, concentrat...