cAMP-activated chloride channel in the basolateral membrane of the thick ascending limb of the mouse kidney.
The properties of an anion-selective channel observed in basolateral membranes of microdissected, collagenase-treated, cortical thick ascending limbs of Henle's loop from mouse kidney were investigated using patch-clamp single-channel recording techniques. In basal conditions, single Cl- currents were detected in 8% of cell-attached and excised, inside-out, membrane patches whereas they were observed in 24% of cell-attached and 67% of inside-out membrane patches when tubular fragments were preincubated with Forskolin (10(-5) M) or 8-bromo-cAMP (10(-4) M) and isobutylmethylxanthine (10(-5) M). The channel exhibited a linear current-voltage relationship with conductances of about 40 pS in both cell-attached and cell-free membrane configurations. A PNa+/PCl- ratio of 0.05 was estimated in the presence of a 142/42 mM NaCl concentration gradient applied to inside-out membrane patches. Anionic selectivity of the channel followed the sequence Cl- greater than Br- greater than NO3- much greater than F-; gluconate was not a permeant species. The open-state probability of the channel increased with membrane depolarization in cell-attached, i.e., in situ membrane patches. In excised, inside-out, membrane patches, the channel was predominantly open with the open-state probability close to 0.8 over the whole range of potentials tested (-60 to +60 mV). The channel activity was not a function of internal calcium concentration between 10(-9) and 10(-3) M. We suggest that this Cl- channel, whose properties are distinct from those in other epithelia, could account for the well-documented conductance which mediates Cl- exit in the basolateral step of NaCl absorption in thick ascending limb of Henle's loop.
Paulais
M
M
INSERM U, 323, Faculté de Médecine Necker, Paris, France.
Teulon
J
J
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D004553:Electric Conductivity; D066298:In Vitro Techniques; D007684:Kidney Tubules / Q000378:metabolism*; D008138:Loop of Henle / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice
D018118:Chloride Channels; D002712:Chlorides; D008565:Membrane Proteins; D005576:Colforsin; D000242:Cyclic AMP; D015056:1-Methyl-3-isobutylxanthine