K+ channels in the basolateral membrane of rat cortical collecting duct.
Impalement studies in isolated perfused cortical collecting ducts (CCD) of rats have shown that the basolateral membrane possesses a K+ conductive pathway. In the present study this pathway was investigated at the single-channel level using the patch-clamp technique. Patch-clamp recordings were obtained from enzymatically isolated CCD segments and freshly isolated CCD cells with the conventional cell-free, cell-attached and the cell-attached nystatin method. Two K+ channels were found which were highly active on the cell with a conductance of 67 +/- 5 pS (n = 18) and 148 +/- 4 pS (n = 21) with 145 mmol/l K+ in the pipette. In excised patches the first channel had a conductance of 28 +/- 2 pS (n = 15), whereas the second one had a conductance of 85 +/- 1 pS (n = 53) at 0 mV clamp voltage with 145 mmol/l K+ on one side and 3.6 mmol/l K+ on the other side of the membrane. So far it has not been possible to characterize the smaller channel further. Excised, and with symmetrical K+ concentrations of 145 mmol/l, the intermediate channel had a linear conductance of 198 +/- 19 pS (n = 5). After excision in the inside-out configuration the open probability (Po) of this channel was low (0.18 +/- 0.05, n = 13) whereas in the outside-out configuration this channel had a threefold higher Po (0.57 +/- 0.04, n = 12). Several inhibitors were tested in excised membranes. Ba2+ (1 mmol/l), tetraethylammonium (TEA+, 10 mmol/l) and verapamil (0.1 mmol/l) all blocked this channel reversibly.(ABSTRACT TRUNCATED AT 250 WORDS)
Hirsch
J
J
Albert-Ludwigs-Universität, Physiologisches Institut, Freiburg, Germany.
Schlatter
E
E
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D018999:Charybdotoxin; D005260:Female; D006863:Hydrogen-Ion Concentration; D007672:Kidney Cortex / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D008564:Membrane Potentials; D008566:Membranes / Q000378:metabolism / Q000502:physiology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012604:Scorpion Venoms / Q000494:pharmacology
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D012604:Scorpion Venoms; D018999:Charybdotoxin; D000255:Adenosine Triphosphate