Volume-activated chloride channels in HeLa cells are blocked by verapamil and dideoxyforskolin

Publisher Website
Google Scholar
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 μM 5-nitro-2-(3-phenylpropylamino)-benzoic acid and by 100 μM 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[γS] and Mg2+-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.