title: Sodium-dependent inhibition of the epithelial sodium channel by an arginyl-specific reagent.
abstract: Effects of the arginyl- and lysyl-specific reagent phenylglyoxal (PGO) on the epithelial Na+ channel were evaluated by measuring the amiloride-blockable 22Na+ fluxes in membrane vesicles derived from the toad bladder epithelium. Incubating whole cells or isolated membranes with PGO readily and irreversibly blocked the channel-mediated tracer flux. Na+ ions present during the interaction of membranes with PGO could protect channels from inactivation by PGO. This effect required the presence of Na+ at the luminal side of the membrane and was characterized by an IC50 of 79 mM Na+. Amiloride, too, could desensitize channels to PGO, but its effect was significant only when whole cells were interacted with the protein-modifying reagent. The data are compatible with a model in which the conductive path of the channel contains a functional arginine, possibly forming a salt bridge with a carboxylic group, which is involved in Na+ translocation and amiloride binding. It was also shown that the augmentation of transport induced by incubating whole cells in Ca2+-free solution (Garty, H., and Asher, C. (1985) J. Biol. Chem. 260, 8330-8335) involves the activation or recruitment of channels that are not vulnerable to PGO prior to incubation.
mesh_terms: D000447:Aldehydes / Q000494:pharmacology*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002024:Bufo marinus; D002462:Cell Membrane / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D005260:Female; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D010658:Phenylglyoxal / Q000378:metabolism / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology*; D012979:Sodium Radioisotopes; D001743:Urinary Bladder / Q000378:metabolism*
chemical_list: D000447:Aldehydes; D007473:Ion Channels; D008565:Membrane Proteins; D012979:Sodium Radioisotopes; D011189:Potassium Chloride; D000584:Amiloride; D012964:Sodium; D010658:Phenylglyoxal