LONGITUDINAL OBSERVATIONS OF MONOAMINE-OXIDASE-B IN ALCOHOLICS - DIFFERENTIATION OF MARKER CHARACTERISTICS

The marker characteristics of monoamine oxidase B (MAO B) in human pla telets were investigated in a clinical study of 59 alcoholics (diagnos ed according to the criteria of ICD-10) observed over a period of 6 mo nths. Demographic and family history were obtained by a structured int erview, including the substance abuse section of CIDI (Composite Inter national Diagnostic interview). The patient's personality was assessed by Cloninger's Tridimensional Personality Questionnaire (TPQ). Blood samples were first drawn during chronic intoxication (day of admission to the hospital for detoxication), after short-term abstinence (8 day s later), medium-term (3 months later), and long-term abstinence (6 mo nths later). A group of 22 matched healthy nonalcoholics served as con trols studied under sober conditions and during acute intoxication (4 hr after ingestion of 1 g ethanol/kg body weight). All platelet sample s were investigated with 6 kynuramine concentrations as substrate (flu orometric assay) in the absence and presence of 200 mM ethanol (ETOH) in vitro. MAO B activity was significantly reduced in alcoholics durin g chronic intoxication (V-max: 2.70 +/- 0.15 nmol/min/mg protein) comp ared with sober(V-max: 3.25 +/- 0.23 nmol/min/mg protein) and acutely intoxicated controls that turned to normal during abstinence. However, MAO B activity obtained during medium- and long-term abstinence was s ignificantly lowered in patients with high novelty-seeking and impulsi veness scores in the TPQ, a history of suicide attempts, or an alcohol ic mother. The affinity of MAO B (6, values) was unchanged in alcoholi cs at any time investigated. Addition of ETOH in vitro reduced the aff inity. This effect was less pronounced when the blood had been obtaine d during chronic intoxication and after short-term abstinence, suggest ing tolerance toward ETOH. It is demonstrated that reduced MAO B value s may serve as state and trait markers of alcoholism and that they can be disentangled in a longitudinally designed study.