title: Hypotonicity activates a native chloride current in Xenopus oocytes.
abstract: Xenopus oocytes are frequently utilized for in vivo expression of cellular proteins, especially ion channel proteins. A thorough understanding of the endogenous conductances and their regulation is paramount for proper characterization of expressed channel proteins. Here we detail a novel chloride current (ICl.swell) responsive to hypotonicity in Xenopus oocytes using the two-electrode voltage clamp technique. Reducing the extracellular osmolarity by 50% elicited a calcium-independent chloride current having an anion conductivity sequence identical with swelling-induced chloride currents observed in epithelial cells. The hypotonicity-activated current was blocked by chloride channel blockers, trivalent lanthanides, and nucleotides. G-protein, cAMP-PKA, and arachidonic acid signaling cascades were not involved in ICl.swell activation. ICl.swell is distinct from both stretch-activated nonselective cation channels and the calcium-activated chloride current in oocytes and may play a critical role in volume regulation in Xenopus oocytes.
authors.affiliation: Department of Pharmacology, Mayo Foundation, Rochester, Minnesota 55905.
authors.forename: M J
authors.initials: MJ
authors.lastname: Ackerman
authors.forename: K D
authors.initials: KD
authors.lastname: Wickman
authors.forename: D E
authors.initials: DE
authors.lastname: Clapham
mesh_terms: D000818:Animals; D001711:Biotransformation / Q000187:drug effects; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004594:Electrophysiology; D005260:Female; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology; D008674:Metals, Rare Earth / Q000494:pharmacology; D009711:Nucleotides / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism*; D009994:Osmolar Concentration; D014982:Xenopus laevis
chemical_list: D018118:Chloride Channels; D008674:Metals, Rare Earth; D009711:Nucleotides; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid