Phase delay of the rhythm of 6-sulphatoxy melatonin excretion by artificial light.
The purpose of this study was to investigate the effect of bright artificial light exposure on the rhythms of 6-sulphatoxy melatonin and cortisol excretion in urine. Six healthy males were exposed to light (greater than 3,000 lux) from 1900 to 0200 h (sunset 1928 h) on one occasion. The artificial light delayed the onset of 6-sulphatoxy melatonin excretion. On the next evening the onset of 6-sulphatoxy melatonin excretion in normal light/darkness was delayed by 1 h. The timing of the peak excretion of cortisol was not affected by the light treatment; however, cortisol excretion rate was maintained at a significantly higher rate in the morning and afternoon after the treatment. These results demonstrate the inhibitory action of high intensity light in humans and suggest that one 6-h period of extra light in the evening can phase delay the melatonin onset.
D000328:Adult; D002940:Circadian Rhythm / Q000528:radiation effects*; D006801:Humans; D006854:Hydrocortisone / Q000652:urine; D008027:Light; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives* / Q000652:urine; D010870:Pineal Gland / Q000502:physiology* / Q000528:radiation effects
D008550:Melatonin; C012365:6-hydroxymelatonin; D006854:Hydrocortisone