[Evaluation of structuro-functional heterogeneity of isolated mitochondria from the normal and the ischemic myocardium]

Abstract

The structural and functional heterogeneity of mitochondria isolated from intact and ischemic (after 60 min exposure at 37 degrees C) rabbit myocardium was evaluated. In the presence of cytochrome c. a relatively high (260 +/- 26 ng at O/min . mg of protein) rate of rotenone-sensitive NADH oxidation was observed, which was increased in ischemia. Cytochrome c stimulated the increase of NADH oxidation in mitochondria of normal and ischemic myocardium by the factors of 3.5 and 3.4, respectively. Succinate oxidation in the presence of bromthymol blue in normal and ischemic myocardium mitochondria was activated by cytochrome c 3.3- and 2.9-fold, respectively. The percentage of mitochondria with both structurally damaged membranes was 15% and 25% in normal and ischemic myocardium preparations, respectively. In the absence of ADP, cytochrome c contributed to the increase of the succinate oxidase activity in ischemic mitochondria; that in the 3rd state was inhibited in ischemia and normalized by cytochrome c. A principle was proposed for estimating the percentage of mitochondria with damaged outer membranes, the indices being equal to 34% in control and to 56% in ischemic myocardium. Evidence was obtained suggesting that this mitochondrial fraction was characterized by lowered coupling and absence of rotenone-sensitive NADH: oxidase activity. The percentage of intact mitochondria, in which succinate oxidation is inhibited by bromthymol blue and does not need exogenous cytochrome c, is 51% in control and 19% in ischemic myocardium mitochondria.