title: Volume-activated chloride channels in HeLa cells are blocked by verapamil and dideoxyforskolin.
abstract: The possible role of Cl- currents in regulatory volume decrease processes has been explored in HeLa cells using the whole-cell recording mode of the patch-clamp technique. Cells showed very small currents in voltage-clamp experiments performed with Cl(-)-rich, permeant-cation-free (N-methyl-D-glucamine replacement) intracellular and bathing solutions. Exposure of the cells to hypotonic solutions visibly swelled the cells and activated, reversibly, an outward rectifying Cl- current, which decayed at the most depolarised voltages used. Replacement of extracellular Cl- by a series of halide anions, SCN- and gluconate was consistent with an anion selectivity sequence: SCN- > I- > Br- > Cl- > F- > gluconate. The volume-regulated Cl- current was effectively inhibited by 100 microM 5-nitro-2-(3-phenyl-propylamino)-benzoic acid and by 100 microM 4,4'-diisothiocyanotostilbene-2,2-disulphonic acid, substances known to block Cl- channels in a variety of cells. Chloride current activation by hypotonicity was dependent on the presence of ATP in the intracellular solution and this requirement could be replaced by the non-hydrolysable analogue ATP[gamma S] and Mg(2+)-free ATP. The data suggest that the channels responsible for the current described are involved in the regulatory volume decrease in HeLa cells. The characteristics of this Cl- current are similar to those of the current associated with expression of multidrug resistance P-glycoprotein. Furthermore, the currents in HeLa cells were inhibited rapidly and reversibly by verapamil and 1,9-dideoxyforskolin, which are known to inhibit P-glycoprotein function.
authors.affiliation: AFRC Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, UK.
authors.forename: M
authors.initials: M
authors.lastname: Díaz
authors.forename: M A
authors.initials: MA
authors.lastname: Valverde
authors.forename: C F
authors.initials: CF
authors.lastname: Higgins
authors.forename: C
authors.initials: C
authors.lastname: Rucăreanu
authors.forename: F V
authors.initials: FV
authors.lastname: Sepúlveda
mesh_terms: D000255:Adenosine Triphosphate / Q000502:physiology; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000031:analogs & derivatives* / Q000494:pharmacology; D006367:HeLa Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D006801:Humans; D007038:Hypotonic Solutions; D007473:Ion Channels / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins / Q000187:drug effects*; D009995:Osmosis; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D018118:Chloride Channels; D002712:Chlorides; D007038:Hypotonic Solutions; D007473:Ion Channels; D008565:Membrane Proteins; D005576:Colforsin; D000255:Adenosine Triphosphate; D014700:Verapamil; C047983:1,9-dideoxyforskolin