REVERSIBLE ULTRASTRUCTURAL ALTERATIONS IN THE MYOCYTIC MITOCHONDRIA OF ISOLATED RAT HEARTS INDUCED BY OXYGEN RADICALS

The present study focuses on reversible mitochondrial ultrastructural alterations in myocardial myocytes that correspond or accompany revers ible metabolic depression observed after oxygen radical exposure. The myocytic mitochondrial membranes and matrix of isolated Langendorff-pe rfused rat hearts were examined by semiquantitative morphometry using the electron micrograph as unit. The hearts were exposed to either sta ndard perfusion (group A), 10 min of oxygen radicals together with sup eroxide dismutase and catalase followed by 35 min of recovery (group B ), 10 min of oxygen radicals alone (group C), or 10 min of oxygen radi cals followed by 35 min of recovery (group D). Mitochondrial ultrastru ctural alterations were detected in only a few micrographs in groups A and B. The frequency of micrographs with mitochondrial ultrastructura l alterations was 69% in group C and 62% in group D. In the group expo sed to 10 min of oxygen radicals without recovery (group C) condensed pentalaminar membranous profiles arranged in parallel, interpreted to be closely adhering cristae, were detected in the intracristal compart ment of myocytic mitochondria in 50% of the micrographs. The cristal a dhesions were associated with other mitochondrial ultrastructural chan ges. Cristal adhesions were not present in group A or B, and were rare ly found in the group exposed to 10 min of oxygen radicals followed by 35 min of recovery (group D). Thus, the cristal adhesions appear to b e reversible alterations caused by exposure to oxygen radicals.