title: Effects of changes in serosal chloride on electrical properties of toad urinary bladder.
abstract: Conventional microelectrode and tracer flux techniques were used to study the effects of reduction in serosal chloride concentration ([Cl]s) on the electrical properties of toad urinary bladder epithelium. Reduction in [Cl]s resulted in a transient change in transepithelial potential (Vms) (and of apical and basolateral membrane potentials) that was inversely dependent on the base-line values of those potentials. In all cases, however, there was a decrease in transepithelial resistance (Rt) that was explained by an increase in the sodium conductance of the apical membrane. In tissues in which the transepithelial potential increased, there was a rise in the active mucosal-to-serosal sodium flux. The increase in conductance was directly related to the increase in short-circuit current. The changes in Vms and Rt brought about by reduction in [Cl]s were prevented by agents known to modify sodium transport, including low mucosal sodium concentration, addition of amiloride or amphotericin B to the mucosal solution, or of ouabain to the serosal solution. The results are best explained by a primary effect of chloride reduction on sodium extrusion across the basolateral membrane, with a secondary increase in apical sodium conductance. In addition, the data provide new evidence for the existence of a basolateral chloride conductance pathway.
mesh_terms: D000818:Animals; D002025:Bufonidae; D002122:Calcium Chloride / Q000494:pharmacology; D002712:Chlorides / Q000502:physiology*; D004553:Electric Conductivity; D004594:Electrophysiology; D004848:Epithelium / Q000502:physiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D012964:Sodium / Q000378:metabolism; D001743:Urinary Bladder / Q000502:physiology*
chemical_list: D002712:Chlorides; D012964:Sodium; D002122:Calcium Chloride