Key result
Delayed diazoxide fails to prevent myocyte swelling during stress and reduces contractility compared to control.
Why the study?
The cardioprotective potential of diazoxide when administered after the onset of stress in isolated mouse and human myocytes was unknown.
Does Diazoxide preserve myocyte volume and contractility when administered after the onset of stress in isolated myocytes?
Does Diazoxide preserve myocyte volume and contractility when administered after the onset of stress in isolated myocytes?
The cardioprotective benefits of diazoxide on myocyte volume and contractility are lost if it is not administered prior to or exactly at the onset of cellular stress.
Late diazoxide after stress onset fails to protect isolated myocytes; leaves open the precise timing window for KATP opener cardioprotection in vivo.
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. STUDY DESIGN: 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.
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Janjua et al. (2014) studied Myocardial stress (isolated myocytes). Diazoxide vs. Control Tyrode's solution or stress alone was evaluated on Myocyte volume and contractility (p=<0.05). Diazoxide did not prevent significant myocyte swelling during stress when administered 10 or 20 minutes after the onset of stress, and contractility declined compared to control.
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