title: A potassium channel in the apical membrane of rabbit thick ascending limb of Henle's loop.
abstract: We used the patch-clamp technique to study the activity of single potassium channels in the apical membrane of isolated thick ascending limbs of Henle's loop (TAL) of rabbit kidneys. In cell-attached patches with NaCl Ringer or high-K+ solution in the bath and 140 mM K+ in the pipette, an inwardly rectifying K+ channel was observed with an inward slope conductance of 22.0 +/- 0.5 pS and outward slope conductance of 10.2 +/- 0.3 pS at 22 degrees C (n = 15). The channel was highly selective for K+, with a calculated permeability ratio for K(+)-to-Na+ of 20:1 (n = 4). The open probability (Po) of the channel was 0.89 +/- 0.03 (n = 15) and was not voltage dependent. In inside-out patches with 140 mM K+ in both the bath and the pipette solutions, both Po and conductance of the channel were similar to that in cell-attached patches. Addition of 0.1 mM Ba2+ to the pipette solution reduced Po of the channel in a voltage-dependent manner. Lowering the pH of the bath solution from 7.4 to 6.9 or increasing Ca2+ concentration from 0 to 0.5 mM in inside-out patches did not alter either Po or conductance of the channel. Addition of 2 mM ATP to the bath solution completely inhibited channel activity. This ATP-induced inhibition was fully reversible and was found to be dependent on the ratio of ATP to ADP, since adding 1 mM ADP to the bath solution relieved the ATP-induced blockade. The property of this small-conductance K+ channel make it a likely candidate for recycling of K+ across the apical membrane of TAL of the rabbit kidney. ATP and ADP are possible intracellular regulators of the channel's activity.
authors.affiliation: Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510.
authors.forename: W H
authors.initials: WH
authors.lastname: Wang
authors.forename: S
authors.initials: S
authors.lastname: White
authors.forename: J
authors.initials: J
authors.lastname: Geibel
authors.forename: G
authors.initials: G
authors.lastname: Giebisch
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004553:Electric Conductivity; D005260:Female; D007684:Kidney Tubules / Q000378:metabolism*; D008138:Loop of Henle / Q000378:metabolism* / Q000648:ultrastructure; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism
chemical_list: D015221:Potassium Channels; D001464:Barium; D000255:Adenosine Triphosphate; D012964:Sodium; D002118:Calcium