Plasma Amino Acid Patterns in Alcoholism: The Effects of Ethanol Loading

Tryptophan metabolism in alcoholism

“…That this is so is strongly suggested from circulating Trp concentration and Trp : CAA determinations. Thus, a lower circulating Trp concentration in alcoholics has been a consistent finding of many studies (Siegel et al 1964;Hjorth et al 1981;Branchey et al 1984;Diehl et al 1986;Buydens-Branchey et al 1989). In the study by Siegel et al (1964), however, no information on the duration of abstinence of the alcoholic subjects was given, whereas in the other four studies, measurements were made at times after abstinence varying between 7 and 12 d in one study and up to 42 d in another.…”

“…In one (Pietraszek et al 1991), no changes in blood Trp concentration were observed at 45 min after drinking whisky (though the zero-time value was not reported), whereas in the other two studies (Siegel et al 1964;Eriksson et al 1983), a decrease was demonstrated. In these latter two studies, sampling was performed at time-intervals after drinking longer than 45 min, suggesting that it was too early after alcohol consumption for Pietraszek et al (1991) to demonstrate a significant decrease, given also our own more detailed (3 h) time-course study .…”

“…Only four published studies have assessed indirectly the effects of chronic alcohol intake on this pathway in non-abstinent alcoholics. In the first of these studies, Siegel et al (1964) showed that, whereas serum Trp concentration was decreased in control subjects following acute ethanol loading, no decrease was observed in chronic alcoholics, thus implying a possible inhibition of liver TP activity, as discussed above. Evidence for a disturbance of this pathway by chronic alcohol consumption was subsequently provided by the demonstration (Walsh et al 1966) that, within 24 h of cessation of alcohol consumption, chronic alcoholic subjects excreted decreased amounts of kynurenine metabolites in urine following an oral Trp load.…”

“…In the study by Siegel et al (1964) of a group of alcoholics, acute ethanol intake did not lower plasma Trp concentration. It should be noted that fasting plasma Trp concentration was already lower in the alcoholic, compared with the control, group in this study (a finding which will be discussed further later; see p. 141).…”

“…Some studies, however, have been performed in shorter-term abstinence (< 3 months, usually 2-3 weeks or earlier). Thus serum Trp concentration was found to be lower in recently abstinent alcoholics, compared with controls (Siegel et al 1964;Branchey et al 1984;Diehl et al 1986), and in 1-d abstinent alcoholics, compared with subsequent days up to day 42 (Buydens- Branchey et al 1989). As stated above, Hjorth et al (1981) observed a lower serum Trp concentration following Trp loading in alcoholics during the first 24 h of withdrawal, but not in other patients examined at subsequent time intervals.…”