Postischaemic reperfusion injury in the isolated rat heart: effect of ruthenium red

Abstract

The aim was to investigate the effect of attenuating mitochondrial calcium uptake with ruthenium red on myocardial function and the resultant necrosis following prolonged ischaemia and reperfusion in isolated rat hearts. Mitochondrial dysfunction, secondary to increased calcium uptake, has been implicated as an important mediator of reperfusion injury in the heart. To examine the role of mitochondrial calcium uptake in mediating ischaemic and reperfusion injury, isolated rat hearts were perfused with ruthenium red (n = 6), a polysaccharide dye which inhibits calcium uptake by mitochondria, and were compared to control perfused hearts (n = 7). After stabilisation, hearts were subjected to 60 min no flow ischaemia, immediately followed by 40 min reperfusion. Hearts were used from male Wistar rats weighing 300-350 g. Cardiac high energy phosphates (ATP, phosphocreatine, inorganic phosphate) and pH were continuously monitored during ischaemia and reperfusion using phosphorus magnetic resonance spectroscopy. Contractility (dP/dT), coronary flow, creatine kinase release, and the time to the onset of ischaemic contracture were also measured. No differences in metabolic abnormalities or time to peak contraction during ischaemia were found between groups, suggesting that ruthenium red does not alter the metabolic consequences of ischaemia. However, upon reperfusion, the following differences in the ruthenium red perfused hearts were observed when compared to control hearts (p less than 0.05): ATP and phosphocreatine recovery were more complete, myocardial contractility was greater, coronary flow was greater, and myocyte necrosis was attenuated. Combined with the known inhibitory effect of ruthenium red on mitochondrial calcium uptake, these data suggest that an important component of myocardial injury following ischaemia and reperfusion in the isolated rat heart is the result of mitochondrial calcium accumulation.