Experimental myocardial ischemia. Differential injury of mitochondrial subpopulations

Distinct populations of subsarcolemmal (SS) and inter-fibrillar (IF) rat cardiac mitochondria were studied following 15 and 30 minutes of warm and cold global ischemia. The respiratory control index, state 3, state 4, adenosine diphosphate-oxygen ratio, and specific enzyme activities of these mitochondrial populations were examined. The subsarcolemmar and IF mitochondria were both severely uncoupled and inhibited by warm ischemia. However, IF mitochondria had a higher RCI at each ischemic interval. In cold ischemia, IF mitochondria were not injured compared with control specimens. Subsarcolemmar mitochondria showed a trend towards a lower RCI that was statistically significant at 30 minutes with succinate as a substrate. These data implicate a differential injury of ischemia on the compartmentalized bioenergy metabolism of the myocardial cell.