Department of Biochemistry, University of Allahabad, Allahabad 211002, India.
Neurosci Lett. 2012 Jun 14;518(1):32-5. doi: 10.1016/j.neulet.2012.04.042. Epub 2012 Apr 23.
The pineal hormone melatonin works for the stabilization of biological rhythms, however, it also modulates several other functions such as cardioprotection, thermoregulation and immunomodulation. Melatonin also shows antioxidant activity. The erythrocyte plasma membrane redox system (PMRS) alongwith ascorbate free radical (AFR) reductase is involved in providing protection against oxidative stress. The present work is an ex vivo study addressing RBC PMRS and AFR reductase activities at two different times of the day. The in vitro modulatory effect of melatonin on PMRS and AFR reductase activities is also reported.
The study was carried out on 61 healthy donors of both sexes (aged 20-30). Blood samples were collected at two different timings viz., 10:00 a.m. and 10:00 p.m. PMRS and AFR reductase were determined by methods already reported. The concentration-dependent effect of the melatonin was evaluated by incubating the RBCs with the hormone at different doses.
We present results to show that erythrocyte PMRS and AFR reductase activity are modulated by melatonin, a higher activity (p<0.05) of PMRS and AFR reductase is observed during night when the level of melatonin is high. The effect of in vitro treatment of erythrocytes with melatonin (10(-7) M to 10(-11) M final concentration) shows significant changes during day at a melatonin concentration of 10(-9)M.
To the best of our knowledge this study shows for the first time the circadian rhythmicity of erythrocyte PMRS and AFR reductase activities. The modulatory effect of melatonin on PMRS and AFR reductase opens the possibility of melatonin being used in treatment of such physiological and metabolic dysfunctions that involve photic cues in association with oxidative stress.
松果体激素褪黑素可稳定生物节律，同时还可调节其他功能，如心脏保护、体温调节和免疫调节。褪黑素还具有抗氧化活性。红细胞质膜氧化还原系统（PMRS）和抗坏血酸自由基（AFR）还原酶参与提供对抗氧化应激的保护。本研究是一项针对一天中两个不同时间点红细胞 PMRS 和 AFR 还原酶活性的离体研究。还报告了褪黑素对 PMRS 和 AFR 还原酶活性的体外调节作用。
这项研究在 61 名健康的男女志愿者（年龄 20-30 岁）中进行。血液样本在两个不同时间采集，即上午 10 点和晚上 10 点。PMRS 和 AFR 还原酶的测定采用已报道的方法。通过在不同剂量下孵育红细胞来评估褪黑素的浓度依赖性效应。
我们的研究结果表明，褪黑素可调节红细胞 PMRS 和 AFR 还原酶的活性，当褪黑素水平较高时，夜间（晚上 10 点）观察到 PMRS 和 AFR 还原酶活性更高（p<0.05）。在体外用褪黑素（最终浓度为 10-7 M 至 10-11 M）处理红细胞的效果在白天随着褪黑素浓度为 10-9 M 时显示出显著变化。
据我们所知，这项研究首次显示了红细胞 PMRS 和 AFR 还原酶活性的昼夜节律性。褪黑素对 PMRS 和 AFR 还原酶的调节作用为褪黑素用于治疗涉及与氧化应激相关的光刺激的生理和代谢功能障碍开辟了可能性。
