Platelet-monoamine oxidase activity in Reye's syndrome

Platelet monoamine oxidase activity in alcoholics, alcoholics with drug dependence, and cocaine addicts

The main objective of this investigation was to study the influence of drug dependence on platelet monoamine oxidase (MAO) activity in the presence and absence of alcoholism. One hundred and thirteen admissions to alcohol and drug treatment facilities participated in the study. Twenty-six met the criteria for alcoholism (group I), seventy-eight subjects were alcohol-/cocaine- and cannabis-dependent (group II), and the remaining nine were patients with DSM-III-R diagnosis of cocaine addiction (group III). MAO activity was assayed radiochemically with [14C]tyramine as a substrate (221 microM). The results of this study showed that platelet MAO activity [nmol of product formed x (mg protein)-1 x hr-1] (mean +/- SE) was significantly (p < 0.01) lower in all of these subjects (group I, 5.50 +/- 0.80; group II, 3.90 +/- 0.50; group III, 4.3 +/- 1.60) as compared with controls (14.85 +/- 1.13). Measurements of platelet MAO activity may provide us with a reliable biochemical marker for alcoholism and perhaps addiction to other substances of abuse (i.e., cocaine).

Prevalence of low monoamine oxidase function in alcoholism

Several studies have found a trend for low platelet monoamine oxidase activity (MAO) in alcoholism but with a great deal of overlap in MAO activity of alcoholics versus controls. The main objective of this study was to carry out a detailed assessment of MAO function that included the measurement of key kinetic parameters (i.e., Km, Vmax) in three groups of male subjects: (a) 51 hospitalized chronic alcoholics, (b) 16 recovering alcoholics with 2-10 years of abstinence, and (c) 21 controls. MAO activity was assayed radiochemically with [14C]tyramine as substrate (43-729 microM). The present study demonstrated that alcoholics had low platelet MAO activity (p less than 0.05). Kinetic analysis revealed a substantial reduction (p less than 0.01) in enzyme Vmax values of chronic and recovering alcoholics. Greater than 95% of the alcoholics had Vmax values lower than the smallest value of control subjects. Moreover, 100% of the alcoholics in both groups exhibited exceedingly low Vmax values that were below the 25th percentile of controls. In summary, results of MAO Vmax determinations provided us with a better separation of the alcoholics from controls. Measurements of platelet MAO function that include enzyme Vmax may provide us a reliable biochemical marker for alcoholism.

Salicylate and mitochondrial monoamine oxidase function in Reye's syndrome

The main objective of this investigation was to study the effect of salicylate on platelet mitochondrial monoamine oxidase (MAO) activity isolated from blood of two patients with Reye's syndrome. Comparative studies were made with hospitalized children without Reye's syndrome (n = 27) and healthy children (n = 19) serving as controls. Platelet MAO was measured by a radioenzymatic technique with [14C]tyramine as a substrate. The results of this study showed that salicylate (1.0 mM) caused an appreciable inhibition of the platelet MAO activity of patients with Reye's syndrome at the onset of the illness. This was demonstrated by a greater than 50% reduction in enzyme maximum velocity (Vmax) value. The salicylate MAO-inhibitory effect was maintained throughout the duration of the illness. Salicylate had only a minimal MAO-inhibitory effect on platelets isolated from blood of recovered Reye's syndrome patients, healthy controls, and non-Reye's hospitalized children, and no apparent effect on enzyme Vmax values. These preliminary findings suggest that salicylate-induced mitochondrial injury may affect MAO function in children with Reye's syndrome.