Objective: This study tested the hypothesis that cardioplegic solution supplemented with a nitric oxide donor agent attenuates postischemic cardiomyocytic apoptosis by reduction of mitochondrial complex I up-regulation during global cardiac arrest under cardiopulmonary bypass.
Methods: Twenty-four anesthetized dogs supported by total vented bypass were divided evenly into 4 groups (n = 6) and subjected to 60 minutes of hypothermic ischemia followed by 4 degrees C multidose crystalloid cardioplegic solution infusion. Hearts received either standard crystalloid cardioplegic solution (control), crystalloid cardioplegic solution supplemented with 2 mmol/L L-arginine (L-Arg group), crystalloid cardioplegic solution supplemented with 400 micromol/L N(G)-monomethyl-L-arginine (L-NMMA group), or crystalloid cardioplegic solution supplemented with 100 micromol/L of NO donor compound (3-morpholinosydnonimine; SIN-1 group). After 60 minutes of cardioplegic arrest, the heart was reperfused for a total of 240 minutes after discontinuation of bypass. The occurrence of cardiomyocytic apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling and Western blot analysis of caspase-3.
Results: The occurrence of cardiomyocytic apoptosis was significantly reduced in SIN-1 and L-Arg groups compared with the control group. Mitochondrial complex I mRNA was up-regulated in the control group, and its expression was significantly higher in the L-NMMA group but significantly reduced in the SIN-1 and L-Arg groups. Western blot analysis of Bcl-2 and cytochrome c, an index of mitochondrial damage in postischemic myocardium, revealed a similar pattern.
Conclusion: Nitric oxide-supplemented crystalloid cardioplegic solution diminished postischemic cardiomyocytic apoptosis after global cardiac arrest under cardiopulmonary bypass, possibly via prevention of mitochondrial complex I up-regulation.