Calcium-activated potassium channels in basolateral membranes of colon epithelial cells; reconstitution and functional properties.
Using differential sedimentation, isopycnic and Ficoll-400 barrier centrifugation, basolateral membrane vesicles of surface and crypt cells of the rabbit distal colon were enriched 34- and 9-fold, respectively. 86Rb(+)-uptake into these vesicles, driven by an electrical potential difference, was stimulated by submicromolar Ca2+ activities and inhibited by Ba2+. These findings indicate the presence of Ca2(+)-activated K+ channels. The K+ channels in surface and crypt cell membranes differed with respect to inhibition by the bee venom apamin, the scorpion venom charybdotoxin and tetraethylammonium and exhibited a different pH dependence. Fusion of basolateral membrane vesicles with planar phospholipid bilayers revealed the presence of high-conductance Ba2(+)-sensitive K+ channels which were activated by micromolar Ca2+ and inhibited by crude scorpion venom and trifluoperazine. These K+ channels may be involved in the coupling of apical and basolateral membrane conductances during Na+ absorption and Cl- secretion, but they may also play a role in cell volume regulation.
Department of Pharmacology, University of Vienna.
H
H
Wiener
K
K
Turnheim
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D018999:Charybdotoxin; D003106:Colon / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D066298:In Vitro Techniques; D015221:Potassium Channels / Q000378:metabolism*; D011817:Rabbits; D012413:Rubidium / Q000378:metabolism; D012604:Scorpion Venoms / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D015221:Potassium Channels; D012604:Scorpion Venoms; D018999:Charybdotoxin; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D002118:Calcium