Potent block of volume‐activated chloride currents in endothelial cells by the uncharged form of quinine and quinidine

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Abstract
1 . The effects of quinine and quinidine on the volume-activated chloride current (ICl(vol)) in cultured endothelial cells from bovine pulmonary artery were studied by use of the whole-cell patch-clamp technique. 2 . At pH 7.4 both quinine and quinidine induced a fast and reversible block of ICl(vol) with Ki values of 20 ± 4 μm and 30 ± 10 μm, respectively. 3 . The blocking efficiency of both drugs increased dramatically with increasing extracellular pH, indicating that the blockade is mediated by the uncharged form of quinine and quinidine. 4 . These results suggest a hydrophobic interaction with high affinity between volume-activated chloride channels and uncharged quinine and quinidine within the membrane bilayer of endothelial cells.