Abstract
The effect of a severely stressful situation (sleep restriction and psychological load) on the diurnal changes in novel tryptamine-related compounds (hydroxydiacetyltryptamine, sulphatoxymelatonin, and dihydromelatonin) was evaluated in human subjects for 16days. The subjects were allowed to sleep for 5h on days three through 12 and for 8h on the other days. On days three through 12, the subjects were asked to perform a psychological task. The first two and the last 4days were viewed as control days. A performance test was administered to evaluate the extent of the subjects' fatigue. Total urine was sampled by collecting it into bottles three times a day [(1) during the sleeping period, (2) in the morning, and (3) in the afternoon]. Seven tryptamine-related compounds in urine were assayed using HPLC-fluorometry. The urine melatonin level was high at night and low during the day. In contrast, urinary levels of hydroxydiacetyltryptamine and sulphatoxydiacetyltryptamine were low at night and high during the day. Dihydromelatonin was undetectable in urine during the sleeping period. Sleep restriction and psychological load did not affect diurnal changes in urinary melatonin, hydroxydiacetyltryptamine, sulphatoxydiacetyltryptamine, or N-acetylserotonin levels. The concentrations of hydroxymelatonin and sulphatoxymelatonin in urine did not show diurnal changes and decreased gradually during the experimental days. A principal component analysis confirmed the diurnal changes and suggested two novel metabolic pathways: (1) N-acetylserotonin to sulphtoxydiacetyltryptamine via hydroxydiacetyltryptamine, and (2) melatonin to dihydromelatonin. Severely stressful situations did not affect diurnal changes in melatonin, hydroxydiacetyltryptamine, sulphatoxydiacetyltryptamine, or N-acetylserotonin levels in urine.
Highlights
Three novel indolamine compounds, hydroxydiacetyltryptamine (OH-diatry), sulphatoxydiacetyltryptamine (s-diatry), and dihydromelatonin have been detected in human urine [1]
We carried out the following human experiment, in which the subjects were placed in a stressful condition with sleep restriction and a psychological load
From the present work we report that: (1) the diurnal changes in the tested tryptamine-related compounds in human urine are detectable even in a stressful situation, and (2) some of these compounds are suitable as stress markers after sleep restriction and psychological task-loading
Summary
Hydroxydiacetyltryptamine (OH-diatry), sulphatoxydiacetyltryptamine (s-diatry), and dihydromelatonin (or reduced melatonin; red mel) have been detected in human urine [1]. OH-diatry and s-diatry have diurnal rhythms of excretion in human urine; their concentrations are highest in the daytime and lowest at night. This evidence was obtained in an experiment with young human subjects in a non-stressful situation [1]; the OH-diatry level during the day was 189 ± 320 (lg/mg creatinine [cr]) and that at night was 71.9 ± 64.1 (lg/mg cr). The aim of our present study was to determine whether the diurnal rhythm of the urinary excretion of OH-diatry, s-diatry, and other indolamine compounds were unchanged under a highly stressful situation. We tried to elucidate the interrelationship among indolamine compounds in human urine by performing principal component analysis (PCA)
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