Protein kinase C activation before cardioplegic arrest: beneficial effects on myocyte contractility.
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.


CONCLUSIONS
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.
O
S J
SJ
Division of Cardiothoracic Surgery, Medical University of South Carolina, Charleston 29425, USA.
Cox
M H
MH
Crawford
F A
FA
Spinale
F G
FG
D000818:Animals; D002314:Cardioplegic Solutions; D002478:Cells, Cultured; D004789:Enzyme Activation; D006324:Heart Arrest, Induced; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D009200:Myocardial Contraction / Q000502:physiology*; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology / Q000517:prevention & control*; D009206:Myocardium / Q000166:cytology; D011493:Protein Kinase C / Q000378:metabolism* / Q000502:physiology; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
D002314:Cardioplegic Solutions; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate