title: Cardioprotective benefits of adenosine triphosphate-sensitive potassium channel opener diazoxide are lost with administration after the onset of stress in mouse and human myocytes.
abstract: BACKGROUND
  Adenosine triphosphate-sensitive (KATP) potassium channel opener diazoxide (DZX) maintains myocyte volume and contractility during stress via an unknown mechanism when administered at the onset of stress. This study was performed to investigate the cardioprotective potential of DZX when added after the onset of the stresses of hyperkalemic cardioplegia, metabolic inhibition, and hypo-osmotic stress.
  
  
  METHODS
  Isolated mouse ventricular and human atrial myocytes were exposed to control Tyrode's solution (TYR) for 10 to 20 minutes, test solution for 30 minutes (hypothermic hyperkalemic cardioplegia [CPG], CPG + 100uM diazoxide [CPG+DZX], metabolic inhibition [MI], MI+DZX, mild hypo-osmotic stress [0.9T], or 0.9T + DZX), with DZX added after 10 or 20 minutes of stress, followed by 20 minutes of re-exposure to TYR (±DZX). Myocyte volume (human + mouse) and contractility (mouse) were compared.
  
  
  RESULTS
  Mouse and human myocytes demonstrated significant swelling during exposure to CPG, MI, and hypo-osmotic stress that was not prevented by DZX when administered either at 10 or 20 minutes after the onset of stress. Contractility after the stress of CPG in mouse myocytes significantly declined when DZX was administered 20 minutes after the onset of stress (p < 0.05 vs TYR). Contractility after hypo-osmotic stress in mouse myocytes was not altered by the addition of DZX.
  
  
  CONCLUSIONS
  To maintain myocyte volume homeostasis and contractility during stress (hyperkalemic cardioplegia, metabolic inhibition, and hypo-osmotic stress), KATP channel opener diazoxide requires administration at the onset of stress in this isolated myocyte model. These data have potential implications for any future clinical application of diazoxide.
authors.affiliation: Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, St Louis, MO.
authors.forename: M Burhan
authors.initials: MB
authors.lastname: Janjua
authors.affiliation: Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, St Louis, MO.
authors.forename: Carol M
authors.initials: CM
authors.lastname: Makepeace
authors.affiliation: Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, St Louis, MO.
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Anastacio
authors.affiliation: Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, St Louis, MO.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Schuessler
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO.
authors.forename: Colin G
authors.initials: CG
authors.lastname: Nichols
authors.affiliation: Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, St Louis, MO. Electronic address: lawtonj@wustl.edu.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Lawton
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D003981:Diazoxide / Q000494:pharmacology*; D004195:Disease Models, Animal; D005260:Female; D006324:Heart Arrest, Induced; D006325:Heart Atria / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008297:Male; D051379:Mice; D017202:Myocardial Ischemia / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D009997:Osmotic Pressure; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D015221:Potassium Channels; D014665:Vasodilator Agents; D000255:Adenosine Triphosphate; D003981:Diazoxide