Platelet and liver
monoamine oxidase (
MAO) activity (mean +/- SD) was evaluated in patients with liver-biopsy-proven
Reye's syndrome.
MAO was measured by a radioenzymatic technique with [3H]
tyramine as a substrate. A marked decrease in
MAO activity [3.3 +/- 2.4 nmol of [3H]4-hydroxyphenylacetic
acid formed X (mg protein)-1 X h-1] was observed in platelets on admission in all patients (n = 13) with
Reye's syndrome when compared with hospitalized patients without
liver disease (n = 8) [9.8 +/- 2.5 nmol of [3H]4-hydroxyphenylacetic
acid formed X (mg protein)-1 X h-1] and with
liver disease (n = 10) [9.1 +/- 2.0 nmol of [3H]4-hydroxyphenylacetic
acid formed X (mg protein)-1 X h-1]. Following recovery from the disease, platelet
MAO approached levels that were not significantly different from those of controls. Contrastingly, reduction of hepatic
MAO in
Reye's syndrome was similar to that seen in patients with
liver disease of different etiologies. These studies suggest that reduced platelet
MAO activity is a specific abnormality in
Reye's syndrome, and it may be representative of generalized impairment of mitochondrial function in these patients. Furthermore, the pattern of liver and platelet
MAO activity in
Reye's syndrome may allow for the differentiation of this disease from other hepatopathologic conditions.