The amiloride-sensitive sodium channel.
Net Na+ movement across the apical membrane of high-electrical resistance epithelia is driven by the electrochemical potential energy gradient. This entry pathway is rate limiting for transepithelial transport, occurs via a channel-type mechanism, and is specifically inhibited by the diuretic drug amiloride. This channel is selective for Na+, Li+, and H+, saturates with increasing extracellular Na+ concentration, and is not affected, at least in frog skin epithelium, by changes in apical membrane surface potential. There also appears to be multiple inhibitory regions associated with each Na+ channel. We discuss the possible implications of a voltage-dependent block by amiloride in terms of macroscopic inhibitory phenomena. We describe the use of cultured epithelial systems, in particular, the toad kidney-derived A6 cell line, and the preparation of apical plasma membrane vesicles to study the Na+ entry process. We discuss experiments in which single, amiloride-sensitive channel activity has been detected and summarize current experimental approaches directed at the biochemical identification of this ubiquitous Na+ transport system.
S
S
Sariban-Sohraby
D J
DJ
Benos
D000345:Affinity Labels / Q000378:metabolism; D000450:Aldosterone / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D000906:Antibodies / Q000032:analysis; D001001:Anura; D001696:Biomechanical Phenomena; D002352:Carrier Proteins / Q000276:immunology / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D004553:Electric Conductivity; D004563:Electrochemistry; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects*; D008027:Light; D008954:Models, Biological; D012867:Skin / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D012979:Sodium Radioisotopes; D013329:Structure-Activity Relationship
D000345:Affinity Labels; D000906:Antibodies; D002352:Carrier Proteins; D007473:Ion Channels; D012979:Sodium Radioisotopes; D000450:Aldosterone; D000584:Amiloride; D012964:Sodium