Biochemical Medicine and Metabolic Biology

Biochemical and histopathological studies provide evidence of acute mitochondrial insult in Reye’s syndrome. These studies suggest that the metabolic abnormalities seen in Reye’s syndrome could be due to mitochondrial dysfunction (1). In the liver of Reye’s syndrome patients, the activities of all mitochondrial enzymes assayed to date have been decreased, whereas most of the cytoplasmic enzyme activities are normal. The decrease in mitochondrial enzymes could be due to decreased synthesis, increased degradation, inhibition, inactivation, or loss from liver cells into serum and other biological fluids. Our previous studies (2) and those of Holt et al. (3) showed that the activities of ornithine carbamyl transferase (an enzyme found mainly in the liver mitochondria), were elevated in the serum of many Reye’s syndrome patients, and maximum elevation was seen in Stage I patients. Recent studies by Holt et al. (3) and from our laboratory (4) showed that the activities of glutamate dehydrogenase (a mitochondrial enzyme) were also elevated in the serum of Reye’s syndrome patients. These results suggest that the activities of other mitochondrial enzymes that are known to decrease in the liver of Reye’s syndrome patients may appear in the blood. To test this hypothesis we determined the activities of isocitrate dehydrogenase (EC 1.1.1.42) in the plasma of 12 Reye’s syndrome patients.