title: Activation of Adenosine Triphosphate-regulated Potassium Channels during Reperfusion Restores Isoflurane Postconditioning-induced Cardiac Protection in Acutely Hyperglycemic Rabbits.
abstract: BACKGROUND
  Hyperglycemia is known to inhibit myocardial anesthetic postconditioning. The authors tested whether activation of adenosine triphosphate-regulated potassium (KATP) channels would restore anesthetic postconditioning during acute hyperglycemia.
  
  
  METHODS
  Rabbits subjected to 40-min myocardial ischemia and 3-h reperfusion (ischemia-reperfusion [I/R]) were assigned to groups (n = 10 in each group) with or without isoflurane postconditioning (2.1% for 5 min) in the presence or absence of hyperglycemia and/or the KATP channel agonist diazoxide. Creatine kinase MB fraction and infarct size were measured. Phosphorylated protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS) were assessed. Oxidative stress was evaluated by measuring malondialdehyde, and apoptosis was assessed by dUTP nick-end labeling and activated caspase-3.
  
  
  RESULTS
  Postconditioning significantly reduced myocardial infarct size (26 ± 4% in the isoflurane [ISO] group vs. 53 ± 2% in the I/R group; P = 0.007); whereas, hyperglycemia inhibited this effect (infarct size: 47 ± 2%, P = 0.02 vs. the ISO group). Phosphorylated and eNOS levels increased, whereas malondialdehyde and myocardial apoptosis were significantly lower after isoflurane postconditioning compared with I/R. These effects were inhibited by acute hyperglycemia. Diazoxide restored the protective effect of isoflurane in the hyperglycemic animals (infarct size: 29 ± 2%; P = 0.01 vs. the I/R group), reduced malondialdehyde levels and myocardial apoptosis, but did not affect the expression of phosphorylated Akt or eNOS.
  
  
  CONCLUSIONS
  KATP channel activation restored anesthetic postconditioning-induced myocardial protection under acute hyperglycemia. This effect occurred without increasing Akt or eNOS phosphorylation, suggesting that KATP channels are located downstream to Akt and eNOS in the pathway of isoflurane-induced myocardial postconditioning.
authors: From the Department of Anesthesiology, University of Virginia, Health Sciences Center, Charlottesville, Virginia (J.R., Z.Z.); and Laboratory for Experimental Surgery (N.N.) and the Department of Anesthesiology and Critical Care Medicine, Shaarey Zedeq Medical Center (Y.G.), Hebrew University School of Medicine, Jerusalem, Israel.
authors: Jacob
authors: J
authors: Raphael
authors: Yaacov
authors: Y
authors: Gozal
authors: Nachum
authors: N
authors: Navot
authors: Zhiyi
authors: Z
authors: Zuo
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001786:Blood Glucose / Q000378:metabolism; D052279:Creatine Kinase, MB Form / Q000378:metabolism; D006331:Heart Diseases / Q000503:physiopathology / Q000517:prevention & control*; D006439:Hemodynamics / Q000187:drug effects; D006943:Hyperglycemia / Q000150:complications*; D007328:Insulin / Q000097:blood; D057775:Ischemic Postconditioning / Q000379:methods*; D007530:Isoflurane / Q000494:pharmacology*; D054086:KATP Channels / Q000502:physiology*; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D011817:Rabbits; D017382:Reactive Oxygen Species / Q000378:metabolism; D015424:Reperfusion; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D018685:Anesthetics, Inhalation; D001786:Blood Glucose; D007328:Insulin; D054086:KATP Channels; D017382:Reactive Oxygen Species; D007530:Isoflurane; D052279:Creatine Kinase, MB Form