The selenium-deficient rat heart with special reference to tolerance against enzymatically generated oxygen radicals.

The tolerance against two different levels of enzymatically generated oxygen radicals was studied in isolated Langendorff-perfused hearts from selenium (Se)-deficient and control rats. The glutathione peroxidase activity of the Se-deficient hearts was less than 5% of that of the controls. Examination of the ultrastructure was made after random sampling using morphometric methods. Selenium-deficient hearts demonstrated some areas with myocytes with intracellular oedema. Oxygen radicals (hydrogen peroxide and superoxide) were generated by adding xanthine oxidase for 12 min (high dose: 25 U/l; low dose: 12.5 U/l) and hypoxanthine to the buffer of isolated Langendorff-perfused rat hearts. Left ventricle-developed pressure (LVDP) and high-energy phosphates (ATP and CP) were measured. After the low dose of oxygen radicals, LVDP was reduced to 32.7 +/- 6.5% (mean +/- SEM) of initial values in the Se-deficient group, but only to 58.3 +/- 8.4% in the control group (p less than 0.05). After the high dose, LVDP decreased abruptly to zero in both groups. However, ATP content was significantly (p less than 0.05) lower in Se-deficient than in control hearts. Perfusion with oxygen radicals (low dose) resulted in the appearance of mitochondrial damage in both groups, but intracellular oedema was still present only in the Se-deficient hearts. It is concluded that protection against oxygen radicals was reduced in Se-deficient hearts. This was probably due to loss of myocardial glutathione peroxidase activity.

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.

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 degrees C and kept ischaemic at 15 degrees C for 210 min before being reperfused for 60 min at 37 degrees 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 less than 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) mumol.g-1 dry weight respectively; corresponding values in the supplemented group were 14.4(2.1) and 29.4(3.6) mumol.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 of cellular oedema (Vv(cell oedema/myocyte)) in the supplemented group.(ABSTRACT TRUNCATED AT 250 WORDS)