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Two types of K channel regulated by ATP were observed in pancreatic beta cells from a type-2 diabetic man. One type had a conductance of 67 pS at -70 mV in symmetrical 140 mM KCl and was inhibited by intracellular ATP with a half-maximal concentration of 40 microM. ATP inhibition was antagonised by ADP. Tolbutamide inhibited the whole-cell K currents half-maximally at 25 microM. This channel has properties similar to those found for the ATP-sensitive K channel in rodent and normal human beta cells. The second channel type observed was an ATP-activated K channel. It had a conductance of 37 pS at -70 mV in symmetrical 140 mM KCl and was activated half-maximally by 9 microM intracellular ATP. This channel was unaffected by 1 mM tolbutamide. In cell-attached patches, one beta cell out of four tested responded to 20 mM glucose with depolarization. The role of the ATP-activated K channel with respect to the (patho)physiology of the beta cell is uncertain.


Journal article


Pflugers Arch

Publication Date





265 - 273


Adenosine Diphosphate, Adenosine Triphosphate, Adult, Diabetes Mellitus, Type 2, Electric Conductivity, Electrophysiology, Humans, Islets of Langerhans, Kinetics, Male, Potassium Channels, Potassium Chloride, Tetraethylammonium, Tetraethylammonium Compounds, Tolbutamide