Abstract
1. We analysed the K+ channel composed of the sulphonylurea receptor 2B (SUR2B) and an inwardly rectifying K+ channel subunit Kir6.1 coexpressed in a mammalian cell line, HEK293T, with the patch clamp technique. 2. In the cell-attached configuration, K+ channel openers (pinacidil and nicorandil) activated approximately 33 pS K+ channels (approximately 145 mM external K+), which were inhibited by the sulphonylurea glibenclamide. 3. Although SUR2B forms an ATP-sensitive K+ channel with Kir6.2, whose amino acid sequence is approximately 70% homologous with that of Kir6.1, the K+ channel composed of SUR2B and Kir6.1 surprisingly did not spontaneously open on patch excision in the absence of intracellular ATP. 4. In inside-out patches, uridine diphosphate and guanosine diphosphate induced channel activity, which was inhibited by glibenclamide but not ATP. Intracellular ATP on its own activated the channels. K+ channel openers and intracellular nucleotides synergistically activated the channel. 5. Therefore, the K+ channel composed of SUR2B and Kir6.1 is not a classical ATP-sensitive K+ channel but closely resembles the nucleotide diphosphate-dependent K+ channel in vascular smooth muscle cells.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ATP-Binding Cassette Transporters*
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Adenosine Triphosphate / metabolism*
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Animals
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Cloning, Molecular
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Glyburide / pharmacology
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Guanidines / pharmacology
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Guanosine Diphosphate / pharmacology
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Guanosine Triphosphate / pharmacology
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Hypoglycemic Agents / pharmacology
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KATP Channels
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Macromolecular Substances
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Magnesium / metabolism
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Mice
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Molecular Sequence Data
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Muscle, Smooth, Vascular / metabolism
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Niacinamide / analogs & derivatives
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Niacinamide / pharmacology
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Nicorandil
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Patch-Clamp Techniques
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Pinacidil
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Potassium Channels / genetics
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Potassium Channels / metabolism*
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Potassium Channels, Inwardly Rectifying*
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Receptors, Drug / metabolism*
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Sulfonylurea Compounds / metabolism*
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Sulfonylurea Receptors
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Uridine Diphosphate / pharmacology
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Vasodilator Agents / pharmacology
Substances
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ATP-Binding Cassette Transporters
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Abcc9 protein, mouse
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Guanidines
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Hypoglycemic Agents
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KATP Channels
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Macromolecular Substances
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Potassium Channels
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Potassium Channels, Inwardly Rectifying
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Receptors, Drug
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Sulfonylurea Compounds
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Sulfonylurea Receptors
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Vasodilator Agents
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uK-ATP-1 potassium channel
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Guanosine Diphosphate
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Niacinamide
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Nicorandil
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Uridine Diphosphate
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Pinacidil
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Guanosine Triphosphate
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Adenosine Triphosphate
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Magnesium
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Glyburide