Protection by superoxide dismutase and catalase in the isolated rat heart reperfused after prolonged cardioplegia: a combined study of metabolic, functional, and morphometric ultrastructural variables

SUMMARY

To determine the protective effect during ischaemia and reperfusion of removing oxygen radicals two groups of isolated Langendorff perfused rat hearts were arrested with cardioplegic solution at 4°C and kept ischaemic at 15°C for 210 min before being reperfused for 60 min at 37°C. To remove oxygen radicals superoxide dismutase and catalase were added to the cardioplegic solution and to the buffer during the first 30 min of reperfusion in one group, the other group serving as control. At the end of reperfusion the first derivative of left ventricular developed pressure (dP/dt), coronary flow, high energy phosphate concentrations, and ultrastructure were determined. The ultrastructure was examined using a stereological method based on point counting and the results presented as volume fractions (Vv). DP/dt after 60 min of reperfusion was 61.6(5.6)% (mean(SEM)) of the initial values in the control group and 77.6(3.4)% in the superoxide dismutase and catalase supplemented group (p<0.05). In the supplemented group coronary flow was significantly higher than in the control group but only in the first part of reperfusion. The concentrations of adenosine triphosphate and creatine phosphate in the control group were 9.9(1.0) and 19.6(1.8) μmol·g⁻¹ dry weight respectively; corresponding values in the supplemented group were 14.4(2.1) and 29.4(3.6) μmol·g⁻¹ dry weight. The morphometric examination of the ultrastructure showed no significant difference in interstitial fluid accumulation evaluated by Vv(myocyte/myocardium) measurements and there was no difference in mitochondrial alteration between the two groups. There was, however, a significant reduction in the volume fraction of cellular oedema (Vv(cell oedema/myocyte)) in the supplemented group. This may indicate a protective effect at the cell membrane level. The use of enzymes capable of removing oxygen radicals during and after prolonged hypothermic cardioplegia may partly prevent the loss of cellular integrity and contractile performance.

catalase, ischaemia, oxygen radicals, reperfusion, superoxide dismustase, ultrastructural morphometry