Differential Effects of Reperfusion on Cardiac Mitochondrial Subpopulations in a Preclinical Porcine Model of Acute Myocardial Infarction

FIGURE 1. Representative X-ray fluoroscopic images of coronary artery blood flow before (left), during (middle) and after (right) mid-left anterior descending (LAD) artery occlusion, resulting in ST-elevation myocardial infarction (STEMI) (A) represents the porcine heart at baseline where the red circle denotes the ischemic LAD artery region, and the green circle denotes non-ischemic circumflex artery region. (B) represents the heart when the LAD is occluded, causing ischemia and (C) represents the heart after balloon deflation, resulting in reperfusion.

FIGURE 2. Mitochondrial protein yield as measured by the Bradford assay. Values are represented as median with interquartile range (n = 10/group). No significant differences were found among the four groups. For exact p-values of all group comparisons, please refer to Table 2.

FIGURE 3. Mitochondrial state 3 (top) and state 4 (middle) oxygen consumptions and the respiratory control indices (RCI, state 3/state 4, bottom panels). Left panels (A–C) indicates outcomes (state 3, state 4 and RCI, respectively) using mitochondrial complex I substrates (pyruvate + malate); right panel B (D–F) indicates outcomes (state 3, state 4 and RCI, respectively) using mitochondrial complex II substrate (succinate + rotenone). Values are represented as median with interquartile range (n = 7–10/group). # indicates p ≤ 0.05 (two-tailed) compared to SSM. For exact p-values of all group comparisons, please refer to Table 2.

FIGURE 4. Panel (A): Representative Ca2+ retention capacity assay tracings in terms of Ca2+ Green fluorescence over time. Continuous infusion of 5 mM Ca2+ enters the cuvette over time at the rate of 30 μL min−1. Extra-mitochondrial Ca2+ (in arbitrary fluorescence units [AFU], indicated on the y-axis) is measured by Ca2+ Green. At the start of the experiment, assay buffer containing Ca2+ Green, mitochondria and substrates are added to the cuvette without any external addition of Ca2+. A baseline measurement is taken for about 100 s, after which, a continuous infusion of Ca2+ was started using a syringe pump at the rate of 30 μL min−1. This is indicated by step [1] in magenta arrows. The addition of Ca2+ leads to an immediate spike up until [2], which forms the new baseline for Ca2+ levels within the mitochondria. As Ca2+ is constantly taken up into the mitochondria at a rate approximately equal to the infusion, extra-mitochondrial Ca2+ remains relatively stable. When the maximum calcium retention capacity is reached, mitochondria removes excess Ca2+ out of its membrane, and hence the extra-mitochondrial Ca2+ signal starts increasing. This increase reaches a plateau when the mPTP opens and…

FIGURE 5. Mitochondrial ATP production rate is shown with (A) mitochondrial complex I (pyruvate + malate) and (B) complex II (succinate + rotenone) substrates. Values are represented as median with interquartile range (n = 7–8/group). For exact p-values of all group comparisons, please refer to Table 2.