The circadian rhythm in plasma melatonin concentration of the urbanized man: the effect of summer and winter time

Illnerová, Helena; Zvolský, P; Vaneˇcˇek, Jirˇí

doi:10.1016/0006-8993(85)91342-3

Cited by 106 publications

(39 citation statements)

References 17 publications

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“…The annual change in the acrophase for aMT6s excretion is in agreement with the findings of other workers (Illnerova et al 1985;Kennaway & Royles 1986;Arendt & Broadway 1986), who all reported phase advances in summer. The greatest phase advance, that of 2 h, occurred under the extreme lighting conditions found in the Antarctic (Arendt & Broadway 1986).…”

Section: Discussionsupporting

confidence: 90%

“…Recent evidence has shown that bright light can also phase shift the human melatonin rhythm (Broadway et al 1987;Lewy et al 1987) and the human temperature and cortisol rhythms (Czeisler et al 1986 (Arendt et al 1979;Touitou et al 1984;Martikainen et al 1985;Illnerova et al 1985) and seasonal differenees have been found; with peaks in summer and winter, and troughs in spring and autumn (Arendt et al 1979) and a phase shift in the melatonin profiles, with the summer profile phase advanced by 1 h relative to the winter profile (Illnerova et al 1985).…”

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confidence: 97%

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Annual changes in 6-sulphatoxymelatonin excretion in man

Bojkowski

Arendt

1988

Acta Endocrinologica

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A recently developed RIA for 6-sulphatoxymelatonin, the major urinary metabolite of melatonin, has been used to investigate the annual change in melatonin secretion in humans. Twenty plasma samples were taken from 18 volunteers throughout a 24-h period and simultaneous 6-hourly urine samples were also collected. Plasma melatonin and urinary 6-sulphatoxymelatonin were measured by RIA. 6-Sulphatoxymelatonin assayed in the urine samples was shown to be a good index of the rhythmic characteristics of the plasma melatonin secretion. To study annual changes in excretion four sequential 6-hourly urine samples were collected at monthly intervals from 16 normal volunteers for 13 months. Cosinor curves were fitted to the 6-sulphatoxymelatonin excretion data and the 24-h rhythm was described by the cosinor parameters: amplitude, mesor and acrophase. Significant differences in the acrophase were found during the year. The summer acrophase was phase advanced relative to the winter acrophase by about 1.5 h while intermediate phase positions were observed in spring/autumn. The 24-h excretion of urinary 6-sulphatoxymelatonin was remarkably consistent and there was no annual rhythm. In contrast, the daytime 6-sulphatoxymelatonin excretion between 12.00\p=n-\18.00 h showed a statistically significant seasonal rhythm,

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Section: Discussionsupporting

confidence: 90%

mentioning

confidence: 97%

Annual changes in 6-sulphatoxymelatonin excretion in man

Bojkowski

Arendt

1988

Acta Endocrinologica

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“…Pineal serotonin, the substrate for NAT, and 5-hydroxyindole acetic acid (SHIAA), a serotonin metabolite, show an inverse concentration pattern with highest levels during the day [Mefford et al, 1983;Champney et al, 19841. During the winter (long nights), the nocturnal synthesis of melatonin is reportedly more prolonged than during spring or summer [Hoffmann et al, 1985;Illnerova et al, 1985;Rollag and Niswender, 19761. These patterns are caused by changes in the NAT activity [Klein and Weller, 19701 which is suppressed by light above a certain, species-specific intensity threshold [Reiter, 19851. Even 1 sec light pulses at night inhibit pineal NAT and melatonin [Reiter et al, 19861. In mammals, NAT activity is controlled indirectly by the environmental lightldark cycle [Wurtman et al, 19631, as perceived by the eyes, and also involving the suprachiasmatic nucleus and the superior cervical ganglia.…”

mentioning

confidence: 98%

Pineal gland “magnetosensitivity” to static magnetic fields is a consequence of induced electric currents (eddy currents)

Lerchl

Nonaka

Reíter

1991

Journal of Pineal Research

137

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During the past decade, a number of reports indicated that the mammalian pineal gland is magnetosensitive in terms of spatial orientation. This indication is based on observations that artificial alterations of the direction of the earth's magnetic field (MF) markedly decreased the gland's capability to synthesize melatonin. These findings, however, seem paradoxical since animals as well as humans experience such alterations whenever they turn their heads. Therefore, the potential of the pineal for sensing magnetic fields was re-investigated. During the dark phase, rats were exposed to repeatedly inverted MFs, generated by two identical pairs of Helmholz coils; one pair connected to a power supply automatically, the other pair manually using an integrated potentiometer. Only the pineals of animals exposed to the automatically activated field responded with a reduced activity of the rate-limiting enzyme serotonin-N-acetyltransferase, lower melatonin levels and increases in serotonin and 5-hydroxyindole acetic acid. Hence, MF exposure itself did not affect the pineal. Rather, induced eddy currents in the animals, resulting from rapid On/Off transients of the artificially applied MF, are most likely the explanation.

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“…2). Data in the literature do not fit this paradigm well in humans since the highest levels of melatonin are not observed consistently during the winter months as would be expected due to shortest photoperiod occurring at this time [7][8][9][10], Touitou et al [7] found sea sonal variations of the hormone with differences between young and elderly subjects: plasma melatonin levels were statistically significantly lower in January in young men and in October in elderly subjects ( fig. 3).…”

Section: Pineal Glandmentioning

confidence: 92%

Effects of Ageing on Endocrine and Neuroendocrine Rhythms in Humans

Touitou¹

1995

Horm Res

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Biological rhythms in blood variables are now fairly well documented in young healthy adults whereas reports in elderly subjects are few for obvious reasons including the difficulty of setting up a group of elderly subjects comparable in age and social background and moreover free of major liver, heart, kidney, bone or any other degenerative disease and consequently not requiring medication. We have observed that the parameters characteristic of the biological rhythm may be modified with ageing. However, the modifications are different from one function or variable to the next. Differences in acrophases, mesors and amplitudes could be demonstrated. For instance the acrophase may be phase-advanced in the elderly for plasma cortisol, DHEA-S, 18-OHDOC, the amplitude may be modified for testosterone, 18-OHDOC, proteins, melatonin, gonadotrophins. The administration as a function of time of drugs or agents used as a diagnostic tool made it possible to ascertain the importance of the time structure in this field. Both validity and interpretation of such administration depend upon the timing of the agent administration in the 24-hour scale. Therefore, the temporal organization of the subjects undergoing such treatments should be taken into account. In the near future this kind of investigation on various biological variables may lead to an improvement of the desired drug effects in elderly patients.

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The circadian rhythm in plasma melatonin concentration of the urbanized man: the effect of summer and winter time

Cited by 106 publications

References 17 publications

Annual changes in 6-sulphatoxymelatonin excretion in man

Annual changes in 6-sulphatoxymelatonin excretion in man

Pineal gland “magnetosensitivity” to static magnetic fields is a consequence of induced electric currents (eddy currents)

Effects of Ageing on Endocrine and Neuroendocrine Rhythms in Humans

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