Two types of K(+) channels are present in the apical membrane of the thick ascending limb of the mouse kidney.
We used the patch-clamp technique to study apical K(+) channels in the split-opened thick ascending limb (TAL) of mouse kidneys. We observed a low-conductance K(+) channel in 8 patches and an intermediate-conductance K(+) channel in 11 patches from a total of 135 cell-attached patches with GOmega seals in the apical membrane of the mouse TAL. Open probability (P(o)) of the low-conductance K(+) channel was 0.85 and was not voltage-dependent between -60 mV and 0 mV. P(o) of the intermediate-conductance was 0.6 at a spontaneous cell membrane potential and decreased to 0.4 by 40 mV hyperpolarization. Both the low-conductance and intermediate-conductance K(+) channels were an inwardly rectifying K(+) channel with inward slope conductances of 26 pS and 74 pS between -20 and 20 mV, respectively. The 74-pS K(+) channel was inhibited by 1 mM Ba(2+) and 10 mM tetraethylammonium when they were applied to the bath facing the cytosolic surface of inside-out patches. Furthermore, addition of 1 mM Mg-ATP reversibly reduced the activity of the 74-pS K(+) channel by 90% within 1 min in inside-out patches. A decrease in bath pH from 7.4 to 6.5 completely blocked the 74-pS K(+) channel in inside-out patches. We conclude that two types of K+ channels are present in the apical membrane of the mouse TAL and that the biophysical properties of the apical 74-pS K(+) channel are identical to those in the rat TAL.
Lu
M
M
Department of Pharmacology, New York Medical College, Valhalla, NY 10595, USA.
Wang
W
W
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D055592:Biophysical Phenomena; D001703:Biophysics; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004594:Electrophysiology; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000819:agonists / Q000187:drug effects / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated; D051640:Small-Conductance Calcium-Activated Potassium Channels; D019789:Tetraethylammonium / Q000494:pharmacology
D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496925:Kcnn4 protein, mouse; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D051640:Small-Conductance Calcium-Activated Potassium Channels; D001464:Barium; D019789:Tetraethylammonium; D000255:Adenosine Triphosphate