Permeation properties and modulation of volume-activated Cl(-)-currents in human endothelial cells.
1. We have studied the permeation and pharmacological properties of a recently described volume-activated, calcium-insensitive, small-conductance Cl(-)-channel in endothelial cells from human umbilical vein. 2. The relative permeability for various anions was I- > Cl- approximately Br- > F- > gluconate- (1.63 +/- 0.36: 1:0.95 +/- 0.16:0.46 +/- 0.04:0.19 +/- 0.07, n = 10). 3. 5-Nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) induced a fast and reversible block of the current (Ki = 29 mumol l-1). 4. Extracellular ATP induced a low-affinity block of the current, that showed a small voltage-dependence (K1 = 4.9 mmol l-1 at +80 mV and K1 = 8.2 mmol l-1 at -80 mV). 5. Extracellularly applied arachidonic acid (10 mumol l-1) irreversibly blocked the current in 5 out of 9 cells. This block seems to be non-specific, because other ionic currents, e.g. inwardly rectifying K+ currents, were blocked as well. 6. Tamoxifen induced a high affinity block of the current (K1 = 2.9 mumol l-1). Block and reversal of block were however much slower than with NPPB. 7. Cytotoxic compounds, which are substrates of the P-glycoprotein multidrug transporter, loaded into endothelial cells via the patch pipette, exerted only minor effects on the volume-activated current. Vinblastine and colcemid did not affect the volume-activated current, whereas daunomycin and vincristine induced a slow 'run-down' of the current. 8. The similarity between permeation and pharmacological properties of volume-activated Cl--currents in endothelial cells and those in many other cell types may suggest that they all belong to the same family of volume-activated small-conductance Cl--channels. Evidence that they belong to the class of P-glycoprotein associated Cl--channels is however only marginal, whereas their biophysical characteristics differ significantly from those of the CIC-2 volume-activated Cl--channels.
K.U. Leuven, Laboratorium voor Fysiologie, Belgium.
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Nilius
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Sehrer
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Droogmans
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000032:analysis; D000255:Adenosine Triphosphate / Q000494:pharmacology; D016718:Arachidonic Acid / Q000494:pharmacology; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D007038:Hypotonic Solutions; D009579:Nitrobenzoates / Q000494:pharmacology; D010539:Permeability; D013629:Tamoxifen / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018118:Chloride Channels; D007038:Hypotonic Solutions; D009579:Nitrobenzoates; D013629:Tamoxifen; D016718:Arachidonic Acid; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D000255:Adenosine Triphosphate