Simultaneous functional expression of swelling and forskolin-activated chloride currents in primary cultures of rabbit distal convoluted tubule.
Ionic Cl- currents induced by cell swelling and forskolin were studied in primary cultures of rabbit distal convoluted tubule (DCTb) by the whole-cell patch clamp technique. We identified a Cl- conductance activated by cell swelling with an hyperosmotic pipette solution. The initial current exhibited an outwardly rectifying 1-V relationship, whereas steady state current showed strong decay at depolarized membrane potentials. The ion selectivity was I- > Br- > Cl- > > glutamate. The forskolin-activated Cl- conductance demonstrated a linear I-V relationship and its ion selectivity was Br- > Cl- > I- > glutamate. This last conductance could be related to the CFTR (cystic fibrosis transmembrane conductance regulator) previously identified in these cells. NPPB inhibited both Cl- currents, and DIDS inhibited only the swelling-activated Cl- current. Forskolin had no effect on the activation of the swelling-activated Cl- current. In DCTb cells which exhibited swelling-activated Cl- currents subsequently inhibited by DIDS, forskolin could activate CFTR related Cl- currents. In the continuous presence of I- which inhibited CFTR conductance, forskolin did not modify the swelling-activated current. The results suggest that both Cl- conductances could be co-expressed in the same DCTb cell and that CFTR did not modulate the swelling-activated conductance.
Rubera
I
I
UMR CNRS 6548, université de Nice-Sophia-Antipolis, Nice, France.
Tauc
M
M
Michel
F
F
Poujeol
C
C
Poujeol
P
P
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects; D048429:Cell Size; D002478:Cells, Cultured; D002712:Chlorides / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000502:physiology; D004553:Electric Conductivity; D004594:Electrophysiology; D007686:Kidney Tubules, Distal / Q000166:cytology / Q000502:physiology*; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D011817:Rabbits
D002712:Chlorides; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid