A chloride channel at the basolateral membrane of the distal-convoluted tubule: a candidate ClC-K channel.
The distal-convoluted tubule (DCT) of the kidney absorbs NaCl mainly via an Na+-Cl- cotransporter located at the apical membrane, and Na+, K+ ATPase at the basolateral side. Cl- transport across the basolateral membrane is thought to be conductive, but the corresponding channels have not yet been characterized. In the present study, we investigated Cl- channels on microdissected mouse DCTs using the patch-clamp technique. A channel of approximately 9 pS was found in 50% of cell-attached patches showing anionic selectivity. The NPo in cell-attached patches was not modified when tubules were preincubated in the presence of 10-5 M forskolin, but the channel was inhibited by phorbol ester (10-6 M). In addition, NPo was significantly elevated when the calcium in the pipette was increased from 0 to 5 mM (NPo increased threefold), or pH increased from 6.4 to 8.0 (NPo increased 15-fold). Selectivity experiments conducted on inside-out patches showed that the Na+ to Cl- relative permeability was 0.09, and the anion selectivity sequence Cl(-)--I(-) > Br(-)--NO3(-) > F(-). Intracellular NPPB (10-4 M) and DPC (10-3 M) blocked the channel by 65% and 80%, respectively. The channel was inhibited at acid intracellular pH, but intracellular ATP and PKA had no effect. ClC-K Cl- channels are characterized by their sensitivity to the external calcium and to pH. Since immunohistochemical data indicates that ClC-K2, and perhaps ClC-K1, are present on the DCT basolateral membrane, we suggest that the channel detected in this study may belong to this subfamily of the ClC channel family.
Lourdel
Stéphane
S
Laboratoire de Physiologie, CNRS-FRE 2468, Institut des Cordeliers, 15 rue de l'Ecole de Médecine, 75270 Paris CEDEX 06, France.
Paulais
Marc
M
Marvao
Pedro
P
Nissant
Antoine
A
Teulon
Jacques
J
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D018118:Chloride Channels / Q000737:chemistry / Q000145:classification* / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007686:Kidney Tubules, Distal; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D011493:Protein Kinase C / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D018118:Chloride Channels; D005576:Colforsin; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium