Matthews C D, Guerin M V, Wang X
Department of Obstetrics and Gynaecology, University of Adelaide, Queen Elizabeth Hospital, South Australia.
Clin Endocrinol (Oxf). 1991 Jul;35(1):21-7. doi: 10.1111/j.1365-2265.1991.tb03491.x.
The aims of the study were (1) to examine the human plasma melatonin rhythm at the equinoxes and the solstices in the natural photoperiod (at 35 degrees S); (2) to examine melatonin rhythms in the same subjects under extended darkness conditions to expose any suppressive (gating) effects of light at any time of the year; (3) to undertake a rigorous examination of the relationship between plasma melatonin and the urinary metabolite 6-sulphatoxy melatonin at varying times of the year.
At the equinoxes and solstices, unrestricted subjects had hourly urine collections followed by venous blood sampling taken under natural light conditions for 24 hours. Following a 24 hour interval, a similar collection regime was performed with subjects held under conditions of extended darkness (5 hours darkness prior to natural sunset and following natural sunrise) for a further 24 hours.
Groups of four (minimum) to six female volunteers (age range 18-35 years) were studied, who had a normal lifestyle, no history of depression, and were not taking any medication or recently engaged in shiftwork.
The plasma was assayed for melatonin and the urine samples for 6-sulphatoxy melatonin by radioimmunoassay.
The onset of natural melatonin secretion was delayed until after sunset at all seasons but was earlier in summer, and not different from the time of sunset in extended darkness. The offset of melatonin secretion under natural conditions occurred at sunrise in autumn and winter but was delayed until after sunrise during spring and summer, particularly in extended darkness. No significant changes in the duration of melatonin secretion were observed between seasons nor between the duration of melatonin secretion under natural photoperiod or extended darkness. The measurement of 6-sulphatoxy melatonin proved to be a close indicator of the phase and amplitude of secretion of plasma melatonin. Both onset and offset times of 6-sulphatoxy melatonin were delayed compared to the times when plasma melatonin was detectable/undetectable. A good correlation exists between the total plasma melatonin secretion and that of 6-sulphatoxy melatonin.
The results suggest evidence for a suppressive (gating) effect of light at dawn only during summer which was associated with a phase advance of the onset of melatonin secretion at this time of year. The lack of a major gating effect of environment light on melatonin secretion, and the unchanging duration of secretion through the year in the normally entrained human, highlight differences between the human and those photoperiodic animal species which breed seasonally. Urinary 6-sulphatoxy melatonin proved to be a good indicator of plasma melatonin levels under rigorous examination and is confirmed as a useful clinical measure.
本研究的目的是：（1）在自然光照周期（南纬35度）下，研究春分和秋分时人体血浆褪黑素节律；（2）在相同受试者处于延长黑暗条件下，研究褪黑素节律，以揭示一年中任何时候光照的抑制（闸门）效应；（3）在一年中的不同时间，严格研究血浆褪黑素与尿代谢物6 - 硫酸氧褪黑素之间的关系。
在春分和秋分时，无限制的受试者每小时收集尿液，随后在自然光条件下进行24小时静脉血采样。间隔24小时后，对受试者在延长黑暗条件下（自然日落前5小时至自然日出后）再进行24小时的类似收集程序。
研究了四（最少）至六名女性志愿者（年龄范围18 - 35岁）组成的小组，她们生活方式正常，无抑郁症病史，未服用任何药物，近期也未从事轮班工作。
通过放射免疫分析法测定血浆中的褪黑素以及尿液样本中的6 - 硫酸氧褪黑素。
在所有季节，自然褪黑素分泌的开始均延迟至日落后，但在夏季较早，且与延长黑暗条件下的日落时间无差异。自然条件下褪黑素分泌的结束在秋冬季节发生于日出时，但在春夏季节延迟至日出后，尤其是在延长黑暗条件下。在不同季节之间，以及在自然光照周期或延长黑暗条件下褪黑素分泌的持续时间之间，均未观察到显著变化。6 - 硫酸氧褪黑素的测量结果被证明是血浆褪黑素分泌相位和幅度的密切指标。与血浆褪黑素可检测/不可检测的时间相比，6 - 硫酸氧褪黑素的开始和结束时间均延迟。血浆总褪黑素分泌与6 - 硫酸氧褪黑素的分泌之间存在良好的相关性。
结果表明，仅在夏季黎明时存在光照的抑制（闸门）效应，这与一年中此时褪黑素分泌开始的相位提前有关。环境光对褪黑素分泌缺乏主要的闸门效应，以及在正常同步的人体中全年分泌持续时间不变，突出了人类与季节性繁殖的光周期动物物种之间的差异。经过严格检验，尿6 - 硫酸氧褪黑素被证明是血浆褪黑素水平的良好指标，并被确认为一种有用的临床测量方法。
