Potassium channels in the luminal membrane of rabbit proximal straight tubule. Evidence from vesicle studies.
The characteristics of 86Rb+ fluxes through K+ channels in luminal-membrane vesicles isolated from the pars recta of rabbit proximal tubule were studied. In KCl-loaded vesicles from the pars recta, transient accumulation of 86Rb+ is observed which is modestly inhibited by BaCl2 and blocked by CdCl2. The isotope accumulation is driven by an electrical diffusion potential, as shown in experiments using either these membrane vesicles loaded with different anions, or an outwardly directed Li+ gradient with a Li+ ionophore. The vesicles containing the channel show a cation selectivity with the order K+ greater than Rb+ greater than choline+ greater than or equal to Li+ greater than Na+. The CdCl2-sensitive 86Rb+ flux is dependent on intravesicular Ca2+. Increasing concentrations of Ca2+ gradually decreased the 86Rb+ uptake and at 1 microM-Ca2+ the CdCl2-sensitive isotope flux is nearly abolished.
Jacobsen
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C
Institute of Medical Biochemistry, University of Aarhus, Denmark.
Røigaard-Petersen
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H
Sheikh
M I
MI
D000818:Animals; D001464:Barium / Q000494:pharmacology; D017609:Barium Compounds; D001693:Biological Transport, Active / Q000187:drug effects; D002104:Cadmium / Q000494:pharmacology; D019256:Cadmium Chloride; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008094:Lithium / Q000494:pharmacology; D018021:Lithium Chloride; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D011817:Rabbits; D012414:Rubidium Radioisotopes / Q000378:metabolism; D013997:Time Factors
D017609:Barium Compounds; D002712:Chlorides; D015221:Potassium Channels; D012414:Rubidium Radioisotopes; D002104:Cadmium; C024986:barium chloride; D001464:Barium; D008094:Lithium; D018021:Lithium Chloride; D019256:Cadmium Chloride; D002118:Calcium