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Murine Isolated Heart Model of Myocardial Stunning Associated with Cardioplegic Arrest
Published on: August 6, 2015
Protein kinase C activation before cardioplegic arrest: beneficial effects on myocyte contractility
1Division of Cardiothoracic Surgery, Medical University of South Carolina, Charleston 29425, USA.
Objective:
A potential intracellular mechanism for the protective effects of myocardial preconditioning is the activation of protein kinase C. The present study tested the hypothesis that a brief period of protein kinase C activation before cardioplegic arrest would provide protective effects on myocyte contractility with subsequent reperfusion and rewarming.
Methods:
Left ventricular porcine myocytes were assigned to the following treatments: (1) Protein kinase C/cardioplegia: Protein kinase C activation in myocytes (n = 39) for 3 minutes with a phorbol ester (10(-9) mol/L of phorbol 12-myristate 13-acetate) in oxygenated, normothermic (37 degrees C) cell media. Protein kinase C activation was followed by 2 hours of cardioplegic arrest (K+, 24 mEq/L; HCO3-, 30 mEq/L; 4 degrees C) and a 5-minute reperfusion period (37 degrees C media). (2) Cardioplegia: Myocytes (n = 31), 2 hours of cardioplegic arrest, and a 5-minute reperfusion and rewarming period. Myocyte contractility was measured by means of high-speed videomicroscopy. For comparison purposes, contractile function was examined in myocytes (n = 70) under normothermic control conditions.
Results:
Myocyte shortening velocity was reduced after cardioplegic arrest when compared with normothermic values (22.3 +/- 1.6 vs 48.8 +/- 2.0 microm/sec, p < 0.0001). Protein kinase C activation before cardioplegic arrest normalized myocyte shortening velocity (48.8 +/- 2.5 microm/sec). Co-incubation with phorbol 12-myristate 13-acetate and chelerythrine (10(-6) mol/L), an inhibitor of protein kinase C, before cardioplegic arrest abolished the protective effects of phorbol 12-myristate 13-acetate pretreatment.
Conclusion:
These results suggest that an endogenous means of providing improved myocardial protection during prolonged cardioplegic arrest can be achieved through a brief period of protein kinase C activation.
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