Comparison of cytosolic and mitochondrial hepatic enzyme alterations in Reye's syndrome.

The activities of nine enzymes in liver specimens obtained from four children who had died from Reye's syndrome were compared to the corresponding activities of a control group of four children who had died from unrelated causes. At the 95% significance level, the alterations could be classified into three groups. Five activities [lactate dehydrogenase, alanine aminotransferase, glucose 6-phosphatase, cytochrome oxidase, and malate dehydrogenase (mitochondrial plus cytosolic)] showed no change. Three enzymes [glutamate dehydrogenase, isocitrate dehydrogenase (NADP), and monoamine oxidase] were decreased. One activity (glucose 6-phosphate dehydrogenase) was increased. The malate dehydrogenase isozymes were resolved by electrophoresis, and the two bands were stained and measured. The ratio of cytosolic:mitochondrial enzyme was significantly greater in Reye's syndrome than in the control group. These results lend further support to the view that in Reye's syndrome the impairment of hepatic function is largely confined to the mitochondria. The lowered activity of monoamine oxidase means that the abnormalities extend to the outer mitochondrial membrane. Imbalances of the cytosolic:mitochondrial enzyme activities were evaluated in needle biopsy specimens from four other children under conditions where neurologic abnormalities were less severe. Two patients had elevated ratios of both glutamate:lactate dehydrogenase and cytosolic:mitochondrial malate dehydrogenase activities, and a third had only an abnormal malate dehydrogenase ratio. In contrast to these Reye's syndrome patients, a fourth case admitted with a provisional diagnosis of Reye's syndrome showed no abnormality in either ratio in stage IV coma.