Effects of daytime noise load on the sleep-wake cycle and endocrine patterns in man. III. 24 hours secretion of free and sulfate conjugated catecholamines.

This study was designed to re-examine the circadian profiles of dopamine, noradrenaline and adrenaline in the plasma and to investigate the influence of daytime noise stress on these profiles. Twelve subjects participated in two experimental series of 60 h; during one they were exposed to 85 dB(A) industrial noise from 9:00 to 21:00 h. Blood samples were taken for a period of 24 h at 20 min intervals and the plasma levels of the free and the sulfoconjugated catecholaminergic compounds were simultaneously measured. A significant (p less than 0.001) circadian rhythm was found for free noradrenaline, free adrenaline and conjugated dopamine. Noise stress significantly increased (p less than 0.001) free adrenaline levels during the first 6 h of exposure and lowered (p less than 0.001) free noradrenaline values during the whole time of exposure; dopamine did not respond. It was concluded that strong noise load has effects on the sympatho-adrenomedullary system but the actual release pattern of each catecholaminergic metabolite is controlled by separate determinants.