Two types of potassium channel regulated by ATP in pancreatic B cells isolated from a type-2 diabetic human.
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.
Williams
B A
BA
University Laboratory of Physiology, Oxford, UK.
Smith
P A
PA
Leow
K
K
Shimizu
S
S
Gray
D W
DW
Ashcroft
F M
FM
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000328:Adult; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D004553:Electric Conductivity; D004594:Electrophysiology; D006801:Humans; D007515:Islets of Langerhans / Q000503:physiopathology*; D007700:Kinetics; D008297:Male; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014044:Tolbutamide / Q000494:pharmacology
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D000244:Adenosine Diphosphate; D019789:Tetraethylammonium; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D014044:Tolbutamide