Potent block of Cl- channels by antiallergic drugs.
Two antiallergic drugs, cromolyn and RU 31156, were examined for their potency to block intermediate-conductance Cl- channels. For this, single Cl- channel activities of mucosal-type mast cells (RBL-2H3) and alternatively, of colonic carcinoma cells (HT29) were monitored employing the patch-clamp technique in the inside-out patch configuration. Here we show that intermediate-conductance Cl- channels of either cell type were blocked by both compounds. Cl- channel inhibition occurred by a slow rather than a flickering block and with a Hill coefficient around 1. RU 31156 was about one order of magnitude more potent (IC50 about 1 microM) than cromolyn. The IC50 values of each compound were not significantly different (p < 0.01) in the two cell types. Our data provide evidence for two novel Cl- channel blockers, which may be of further use in Cl- channel characterization as well as purification.
D000818:Animals; D002277:Carcinoma / Q000378:metabolism; D002478:Cells, Cultured; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D004205:Cromolyn Sodium / Q000494:pharmacology*; D004553:Electric Conductivity; D006801:Humans; D007473:Ion Channels / Q000187:drug effects*; D008407:Mast Cells / Q000378:metabolism; D008565:Membrane Proteins / Q000187:drug effects*; D008839:Microelectrodes; D009579:Nitrobenzoates / Q000494:pharmacology; D014966:Xanthenes / Q000494:pharmacology*
D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D009579:Nitrobenzoates; D014966:Xanthenes; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; C016874:RU 31156; D004205:Cromolyn Sodium