A saturable, vasopressin-sensitive carrier for urea and acetamide in the toad bladder epithelial cell.
The permeability of the toad bladder to a series of isotopically labeled nonelectrolytes was determined in the presence of 150 mM unlabeled acetamide. Under these conditions, overall bladder function was unimpaired, as shown by a normal response to vasopressin of short-circuit current and permeability coefficient of [(3)H]water,[(14)C]ethanol, and [(14)C]propionamide. The permeability of the bladder to isotopic acetamide and urea, however, was significantly depressed by unlabeled acetamide, in both the absence and presence of vasopressin. These experiments indicate a competition between unlabeled and isotopic species for binding sites, and show the existence of a saturable, vasopressin-sensitive carrier for urea and acetamide in the epithelial cell membrane.
D000081:Acetamides / Q000378:metabolism* / Q000494:pharmacology; D000577:Amides / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001693:Biological Transport, Active; D002024:Bufo marinus / Q000378:metabolism*; D002247:Carbon Isotopes; D002463:Cell Membrane Permeability; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism; D009995:Osmosis; D011422:Propionates / Q000378:metabolism; D014316:Tritium; D014508:Urea / Q000378:metabolism*; D001743:Urinary Bladder / Q000378:metabolism*; D014667:Vasopressins / Q000494:pharmacology*; D014867:Water / Q000378:metabolism
D000081:Acetamides; D000577:Amides; D002247:Carbon Isotopes; D011422:Propionates; D014867:Water; D014316:Tritium; D014667:Vasopressins; D000431:Ethanol; D014508:Urea