Mitochondrial calcium in hearts subjected to lipid peroxidation with contracture development

In the present study we have investigated isolated rat hearts perfused with oxygen radicals generated by xanthine oxidase and hypoxanthine. The influence of verapamil (1 mg.1(-1] pretreatment on oxygen radical-induced contracture development and decrease in contractility was examined. In addition, we have measured mitochondrial calcium and magnesium levels in control hearts and hearts perfused with oxygen radicals with and without addition of superoxide dismutase (SOD) and catalase. The presence of oxygen radical-induced lipid peroxidation was confirmed by the increased level of conjugated diens in lipid extracts from oxygen radical-perfused hearts. Verapamil prevented contracture development in hearts perfused with oxygen radicals. Diastolic pressure measured with a left ventricle balloon was at the end of the experiments. 18 +/- 3 mm Hg (mean +/- SEM) with verapamil and 66 +/- 9 mm Hg without (p less than 0.001). Perfusion with oxygen radicals resulted in a reduction in mitochondrial calcium from 14.63 +/- 0.93 to 8.26 +/- 0.61 nmol.mg-1 (p less than 0.001) which was partly reversed by superoxide dismutase and catalase. Mitochondrial magnesium levels were unchanged in all groups.