title: Inhibition of the endogenous volume-regulated anion channel (VRAC) in HEK293 cells by acidic di-aryl-ureas.
abstract: The endogenous volume-regulated anion channel (VRAC) from HEK293 cells was pharmacologically characterized using the whole-cell patch-clamp technique. Under isotonic conditions a small (1.3 nS), Ca(2+)-independent Cl conductance was measured. However, swelling at 75% tonicity activated a VRAC identified as an outward-rectifying anion current ( P(l) > P(Cl) > P(gluconate)), which was ATP-dependent and showed inactivation at positive potentials. Activation of this current followed a sigmoid time course, reaching a plateau conductance of 42.6 nS after 12-15 min ( t(1/2) = 7 min). The pharmacology of this VRAC was investigated using standard Cl(-)-channel blockers (NPPB, DIDS, and tamoxifen) as well as a new group (acidic di-aryl ureas) of Cl(-)-channel blockers (NS1652, NS3623, NS3749, and NS3728). The acidic di-aryl ureas were originally synthezised for inhibition of the human erythrocyte Cl(-) conductance in vivo. NS3728 was the most potent VRAC blocker in this series ( IC(50) = 0.40 micro M) and even more potent than tamoxifen (2.2 micro M). NS3728 accelerated channel inactivation at positive potentials. These results show that acidic di-aryl ureas constitute a promising starting point for the synthesis of potent inhibitors of VRAC.
authors.affiliation: NeuroSearch A/S, Pederstrupvej 93, DK-2750, Ballerup, Denmark.
authors.forename: N
authors.initials: N
authors.lastname: Hélix
authors.forename: D
authors.initials: D
authors.lastname: Strøbaek
authors.forename: B H
authors.initials: BH
authors.lastname: Dahl
authors.forename: P
authors.initials: P
authors.lastname: Christophersen
mesh_terms: D001565:Benzoates / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002460:Cell Line; D002478:Cells, Cultured; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000187:drug effects / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007668:Kidney / Q000187:drug effects / Q000196:embryology / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D010671:Phenylurea Compounds / Q000494:pharmacology*; D013777:Tetrazoles / Q000494:pharmacology; D014508:Urea / Q000494:pharmacology
chemical_list: D001565:Benzoates; D002121:Calcium Channel Blockers; D018118:Chloride Channels; C423868:NS 3623; D010671:Phenylurea Compounds; D013777:Tetrazoles; D014508:Urea; C405615:NS 1652