2 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 be ta 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 intracellu lar ATP with a half-maximal concentration of 40 muM. ATP inhibition wa s antagonised by ADP. Tolbutamide inhibited the whole-cell K currents half-maximally at 25 muM. 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 channe l. It had a conductance of 37 pS at -70 mV in symmetrical 140 mM KCl a nd was activated half-maximally by 9 muM intracellular ATP. This chann el was unaffected by 1 mM tolbutamide. In cell-attached patches, one b eta cell out of four tested responded to 20 mM glucose with depolariza tion. The role of the ATP-activated K channel with respect to the (pat ho)physiology of the beta cell is uncertain.