Reduction of ionic strength activates single volume-regulated anion channels (VRAC) in endothelial cells.
We have previously shown that a reduction of intracellular ionic strength is involved in the activation of volume-regulated anion channels (VRAC). Here we show in a single-channel study that VRAC can be activated in a cell-attached patch when the cell interior is dialyzed with a solution of decreased ionic strength. For this purpose, bovine pulmonary endothelial (CPAE) cells) were permeabilized with alpha-staphylotoxin (alphaST) which has a molecular weight cut-off size of 2 kDa. If the ionic strength in the bath solution is reduced from 160 mM to 95 mM, single-channel activity is initiated in cell-attached patches sealed before permeabilization. Conductance is outwardly rectifying with approximately 17 pS at negative and 57 pS at positive potentials. Single-channel currents reverse near the calculated equilibrium potential for Cl-. The averaged current shows inactivation at positive potentials. The current is blocked by 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB). An increase in ionic strength reversibly inhibits current activation. It is concluded that a decrease in ionic strength activates single-channel currents through VRAC rather than shifting the set point of a hypothetical volume sensor.
Sabirov
R Z
RZ
Laboratory of Molecular Physiology, Academy Sciences of Uzbekistan, Tashkent.
Prenen
J
J
Tomita
T
T
Droogmans
G
G
Nilius
B
B
D000818:Animals; D000838:Anions / Q000378:metabolism; D001427:Bacterial Toxins / Q000494:pharmacology; D002417:Cattle; D002448:Cell Adhesion / Q000502:physiology; D002463:Cell Membrane Permeability / Q000502:physiology; D002478:Cells, Cultured; D018118:Chloride Channels / Q000502:physiology; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D015640:Ion Channel Gating / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology* / Q000648:ultrastructure; D008564:Membrane Potentials / Q000502:physiology; D009578:Nitrobenzenes / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011651:Pulmonary Artery / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure; D012996:Solutions
D000838:Anions; D001427:Bacterial Toxins; D018118:Chloride Channels; D007473:Ion Channels; D009578:Nitrobenzenes; D012996:Solutions; C036117:staphylotoxin; C047633:5-(4-nitrophenyl)-2,4-pentadienal