Effects Of Hypoxia/drug Postconditioning On The Expression Of ATP-sensitive Potassium Channel Subunits In Isolated Rat Cardiomyocytes

Objective:ATP-sensitive potassium (KATP) channel is thought to be a mediator of cardioprotection during ischemia—reperfusion, and it potentially comprises pore-forming subunits (Kir6.1 and/or Kir6.2) and sulfonylurea receptor (SUR1 or SUR2) subunits.Methods:In present study, we have applied RT-PCR and western-blot to investigate the effects of cardiac postconditioning on the expressions of KATP channel subunits through the model of isolated rat cardiomyocytes, including Kir6.1 (Kcnj8), Kir6.2 (Kcnj11), SUR1 (Abcc8) and SUR2 (Abcc9). Cardiomyocytes were isolated from male adult Sprague-Dawley rat(250-300g) left ventricle by Langendorff-perfusion and collagenase-Ⅱdigestion. After 45minutes ischemia, cardiac postconditioning was performed through three cycles of ischemia(3min)-reperfusion(3min), and pinacidil (100μM,5min), in the presence or absence of KATP channel blocker glybenclamide(10μM, 10min). And cardiomyocytes were oxygen-incubated for 60min followed by RNA isolation or for 180min followed by protein isolation.Result:The mRNA expressions of Kir6.1,Kir6.2 and SUR2 were significantly increased following cardiac postconditioning with ischemia-reperfusion and pinacidal, and the KATP channels blocker glybenclamide abolished these increases, accordingly western-blot demonstrates similar increases. In contrast, the expressions of SUR1 were decreased under experimental conditions, western-blot showed no significant changes.Conclusion:Cardiomyocytes postconditioning affected the expression of KATP channel subunits differentially, with increases in Kir6.1,Kir6.2 and SUR2 which can be abolished by KATP channels blocker glybenclamide, while the expression of subunit SUR1 changed conversely.