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.

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Allergen-mediated histamine release from human leukocytes represents an important model for in vitro studies of allergic reactions. The purpose of this study was to determine whether the measurement of histamine released in allergic patients by radioenzymatic assay following mixing of their blood with common allergens represents a reliable index for diagnosis of atopic allergy. Three categories of allergens were used: 1) house dust and mite; 2) cat and dog dander; 3) trees, grasses and ragweed mixture. The presence of allergy was established by clinical history and intradermal skin testing in the study group of 150 patients. A significant allergen-mediated histamine release ranging from 4 to 65% of the total blood histamine content was observed in 96% of the patients with skin test sensitivity of greater than or equal to 3+. There was a significant correlation between skin testing and histamine release in terms of the allergens causing the response. Thus, the measurement of histamine by radioenzymatic technique following its release in blood in response to allergen challenge represents a clinically useful in vitro test for the diagnosis of atopic disease.

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