The role of mitochondrial respiratory pathways using different cardioplegic solutions in immature rat hearts: a comparative study on moderate and prolonged ischemic periods
D Verikas, A Mamedov, E Rumbinaite, G Jakuskaite, G Zukaite, P Jakuska, R Benetis, E StankeviciusAbstract
Introduction
To enhance myocardial protection in pediatric cardiac surgery, diverse cardioplegic solutions are employed. Studies suggest that the choice of cardioplegic solution can significantly affect immature myocardial tissue, surpassing the impact of physiological characteristics. Minor defects in the mitochondrial ATP-generating system and oxidative phosphorylation post-cardioplegia can adversely affect cardiac function in immature hearts.
Aim
The aim of this study was to investigate the impact of different cardioplegic solutions on the mitochondrial respiratory pathways in heart tissue of immature rats after moderate (after 1 hour) and prolonged ischemic period (after 3 hours).
Methods
39 male Wistar albino rats (up to 1 month old) underwent median sternotomy, and Custodiol HTK, del Nido, or St. Thomas was infused into the aorta. Hearts were incubated for 1 h and 3 h, then transferred, cut, and homogenized. The homogenate underwent two centrifugations. Mitochondrial energy metabolism was tested using 2 mg equivalents, titrating substrates. Measurements included mitochondrial basal respiration (Mit), ATP-production coupled mitochondrial respiration (ADP), carbonyl cyanide p-trifluoromethoxy phenylhydrazone for maximal respiration (FCCP), and the ratio of cytochrome C complex to ATP-production coupled mitochondrial respiration (CytC/ADP). Three experiments were performed without cardioplegic solution (CP0 group). For moderate and long ischemic periods, 6 experiments each were performed in CP1 (St. Thomas), CP2 (Custodiol HTK), and CP3 (del Nido) groups.
Results
Results in Table 1 reveal CP3's significantly higher mitochondrial activity after 1 hour: 1. Mit: CP3 vs. CP1 (27.8 [17.4; 34.6] vs. 8.5 [7.7; 14.6]; p=0.006); 2. ADP was significantly higher in CP3 vs. CP1 and CP2 (p=0.004); 3. FCCP was significantly higher in CP3 vs. CP1 (173.4 [146.0; 252.9] vs. 71.1 [49.7; 84.4], p=0.001). During prolonged ischemia, only Mit and ADP remained significant, favoring CP3. Analysis showed CP2 and CP3 had higher mitochondrial activity than CP1, while CP3's ADP was significant compared to CP1 (105.7 [86.2; 154.4] vs. 24.2 [11.7; 51.7], p=0.008), with no significant difference versus CP2. CP1 had the highest CytC/ADP ratio, significant versus CP3 (1.6 [1.5; 2.2] vs. 1.2 [1.1; 1.4], p=0.004), indicating outer mitochondrial membrane damage. FCCP lost significance during prolonged ischemia.
Conclusions
Del Nido cardioplegic solution exhibited superior mitochondrial protection in the moderate ischemia period, but these benefits were not as enduring during prolonged ischemia. Custodiol HTK solution demonstrated significant improvement in results over the 3-hour ischemia. These findings underscore the need for further extensive studies to conclusively establish the effectiveness of different cardioplegia types in providing myocardial protection for immature myocardium.For image description, please refer to the figure legend and surrounding text.