Development of new hypoglycemic agents with a novel insulinotropic mechanism and their clinical appkicatior

采用膜片钳技术研究了代谢抑制对格列本脲阻断β细胞ATP敏感的K^+通道（K_<ATP>通道）的影响。在2,4-二硝基苯酚诱导的代谢抑制下，格列本脲对K_<ATP>通道的抑制作用在细胞附着模式下减弱。在低浓度（0.1 μ m）由内而外的ATP模式下，即使使用高剂量的格列本脲，K_<ATP>通道活性也没有完全消除，而在10μ m的ATP模式下，K_<ATP>通道的抑制是剂量依赖性的、完全的。另一方面，Ia类抗心律失常药物苯并喹啉抑制K_<ATP>通道活性呈剂量依赖性，即使在代谢抑制下也能完全阻断该通道。在磺酰脲受体（SUR1）和向内整流K^+通道（Kir6.2）表达的蛋白中，与格列本脲不同，苯并啉直接与Kir6.2结合。因此，在胰腺β细胞胞内ATP减少的情况下，格列本脲对K_<ATP>通道的抑制作用受损，这可能是由于磺酰脲与SUR1结合位点下游的SUR1与Kir6.2之间的信号传递存在缺陷。

The effect of metabolic inhibition on the blocking of beta cell ATP-sensitive K^+ channels (K_<ATP> channels) by glibenclamide was investigated using patch-clamp technique. Inhibition of K_<ATP> channels by glibenclamide was attenuated in the cell-attached mode under metabolic inhibition induced by 2,4-dinitrophenol. Under a low concentration (0.1muM) of ATP applied in the inside-out mode, K_<ATP> channel activity was not fully abolished even when a high dose of glibenclamide was applied, in contrast to the dose-dependent and complete K_<ATP> channel inhibition under 10muM ATP.On the other hand, cibenzoline, a class Ia antiarrhythmic agent, inhibits K_<ATP> channel activity in a dose-dependent manner, and completely blocks it even under metabolic inhibition. In sulfonylurea receptor (SUR1)-and inward rectifier K^+ channel (Kir6.2)-expressed proteins, cibenzoline binds directly to Kir6.2, unlike glibenclamide. Thus, K_<ATP> channel inhibition by glibenclamide is impaired under the condition of decreased intracellular ATP in pancreatic beta cells, probably due to a defect in signal transmission between SUR1 and Kir6.2 downstream of the site of sulfonylurea binding to SUR1.