The proportion of mitochondrial isoenzyme of aspartate aminotransferase is not elevated in Reye's syndrome.

We reexamined a previously reported, highly specific increase in the relative proportion of the mitochondrial isoenzyme of aspartate aminotransferase (AST) in the serum of patients with Reye's Syndrome. Using ion exchange chromatography, we measured mitochondrial, cytosolic, and total AST in serum samples from (1) 10 patients early in the course of Reye's Syndrome; (2) nine controls with normal serum AST; and (3) seven controls with other diseases causing an increase in serum AST. The mitochondrial percentage (2.8 +/- 2.0%) in Reye's Syndrome was significantly lower (P less than 0.05) than that of both the normal control group (6.1 +/- 7.1%) and the group with increased AST (5.6 +/- 4.0%). We thus failed to confirm the previous report of a specific increase in the % of mitochondrial isoenzyme in Reye's Syndrome, and conclude that the % of mitochondrial isoenzyme is not likely to be a useful marker of (or predictor for progression to) Reye's Syndrome.