Deacon S, Arendt J
Endocrinology and Metabolism Group, School of Biological Sciences, University of Surrey, Guildford, UK.
Neurosci Lett. 1994 Feb 14;167(1-2):191-4. doi: 10.1016/0304-3940(94)91059-6.
Melatonin is extensively used as a circadian marker rhythm and thus any factors influencing its concentrations other than endogenous rhythmicity must be assessed. We report here the effects of posture on melatonin concentrations in plasma and saliva. The study was performed during the rising phase of the melatonin rhythm between 21:00 and 01:30 h. From 23:00 h, 7 healthy subjects remained sitting until 24:00 h and in dim light (< 10 lux) until 01:30 h. From 24:00 h, they assumed a different postural position in one of the following stages: Stage 1a: 24:00-00:30 h-standing, 00:30-01:00 h-supine, 01:00-01:30 h-standing; Stage 1b-reverse of Stage 1a; Stage 2a: 24:00-01:30 h-supine; and Stage 2b: 24:00-01:30 h-standing. Blood and saliva samples were obtained every hour from 21:00-24:00 h and then every 10 min from 24:00-01:30 h. Plasma and salivary melatonin concentrations, measured by radioimmunoassay, increased when moving from a supine to a standing position and decreased when these positions were reversed. These changes, as seen with other blood components, can be explained through the influence of gravity which causes a decrease in plasma volume on standing and an increase in plasma volume on lying down.
褪黑素被广泛用作昼夜节律标志物，因此必须评估除内源性节律性之外影响其浓度的任何因素。我们在此报告姿势对血浆和唾液中褪黑素浓度的影响。该研究在褪黑素节律的上升阶段，即21:00至01:30进行。从23:00起，7名健康受试者一直坐着直到24:00，并在昏暗灯光（<10勒克斯）下保持到01:30。从24:00起，他们在以下阶段之一采取不同的姿势：阶段1a：24:00 - 00:30站立，00:30 - 01:00仰卧，01:00 - 01:30站立；阶段1b是阶段1a的反向；阶段2a：24:00 - 01:30仰卧；阶段2b：24:00 - 01:30站立。从21:00至24:00每小时采集一次血液和唾液样本，然后从24:00至01:30每10分钟采集一次。通过放射免疫测定法测量，从仰卧位变为站立位时，血浆和唾液中的褪黑素浓度升高，而姿势反转时则降低。与其他血液成分一样，这些变化可以通过重力的影响来解释，重力导致站立时血浆量减少，躺下时血浆量增加。
