Volume-sensitive basolateral K+ channels in HT-29/B6 cells: block by lidocaine, quinidine, NPPB, and Ba2+.
Volume-sensitive basolateral K+ channels were studied in apically amphotericin B-permeabilized HT-29/B6 monolayers in Ussing chambers with current fluctuation analysis. The basolateral K+ conductance and Lorentzian K+ channel noise were osmotically activated in presence of Cl- concentrations greater than or equal to 74 mM. Under isotonic conditions with 148 mM Cl-, a large transepithelial K+ current of 500 +/- 16.8 microA/cm2 and a spontaneous Lorentzian K+ channel noise with a corner frequency of 29.8 +/- 1.6 Hz (n = 31) were observed. Increasing extracellular osmolalities by addition of sucrose sensitively decreased the K+ current across the basolateral membrane. Half-maximal sucrose concentration was 20 +/- 6 mM for this shrinkage maneuver. The osmotically sensitive K+ pathway was similarly activated with the halide Br- and selective for K+ over Rb+ (4:1). The established K+ channel blockers lidocaine [50% inhibitory concentration (IC50) = 49.0 +/- 3.7 microM], quinidine (IC50 = 10.1 +/- 1.3 microM), and also the chloride channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (IC50 = 114 +/- 2.1 microM) completely inhibited basolateral K+ currents, whereas 46% of K+ current was blocked by barium (IC50 = 95.3 +/- 23.2 microM). Osmotic sensitivity of this K+ conductance made a correction for hypertonic effects of added blockers necessary, and considerable osmotic effects of blockers at commonly used doses were shown. All blockers induced dose dependently additional Lorentzian noise, indicating a direct inhibitory action on basolateral K+ channels. In this human Cl- secretory cell line, volume-sensitive K+ channels are localized only in the basolateral membrane and may modulate osmotic regulation when HT-29 cells swell.
Illek
B
B
Department of Veterinary Physiology, Free University Berlin, Federal Republic of Germany.
Fischer
H
H
Kreusel
K M
KM
Hegel
U
U
Clauss
W
W
D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002463:Cell Membrane Permeability; D002712:Chlorides / Q000378:metabolism; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D004594:Electrophysiology; D006801:Humans; D008012:Lidocaine / Q000494:pharmacology; D009579:Nitrobenzoates / Q000494:pharmacology; D011188:Potassium / Q000037:antagonists & inhibitors* / Q000502:physiology; D015221:Potassium Channels / Q000378:metabolism* / Q000502:physiology; D011802:Quinidine / Q000494:pharmacology; D012413:Rubidium / Q000502:physiology; D014407:Tumor Cells, Cultured
D002712:Chlorides; D009579:Nitrobenzoates; D015221:Potassium Channels; D001464:Barium; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D008012:Lidocaine; D011802:Quinidine; D012413:Rubidium; D011188:Potassium