Mukherjee Sourav, Maitra Saumen Kumar
Department of Zoology, Visva-Bharati University , Santiniketan , India.
Front Endocrinol (Lausanne). 2015 Jul 22;6:112. doi: 10.3389/fendo.2015.00112. eCollection 2015.
Melatonin, following discovery in the bovine pineal gland, has been detected in several extra-pineal sources including gastrointestinal tract or gut. Arylalkylamine N-acetyltransferase (AANAT) is the key regulator of its biosynthesis. Melatonin in pineal is rhythmically produced with a nocturnal peak in synchronization with environmental light-dark cycle. A recent study on carp reported first that melatonin levels and intensity of a ~23 kDa AANAT protein in each gut segment also exhibit significant daily variations but, unlike pineal, show a peak at midday in all seasons. Extensive experimental studies ruled out direct role of light-dark conditions in determining temporal pattern of gut melatoninergic system in carp, and opened up possible role of environmental non-photic cue(s) as its synchronizer. Based on mammalian findings, physiological significance of gut-derived melatonin also appears unique because its actions at local levels sharing paracrine and/or autocrine functions have been emphasized. The purpose of this mini review is to summarize the existing data on the chronobiology and physiology of gut melatonin and to emphasize their relation with the same hormone derived in the pineal in vertebrates including fish.
褪黑素在牛的松果体中被发现后，在包括胃肠道或肠道在内的多个松果体外来源中也被检测到。芳基烷基胺N-乙酰基转移酶（AANAT）是其生物合成的关键调节因子。松果体中的褪黑素是有节律地产生的，在夜间达到峰值，与环境光暗周期同步。最近一项关于鲤鱼的研究首次报道，每个肠道段中褪黑素水平和一种约23 kDa的AANAT蛋白的强度也呈现出显著的每日变化，但与松果体不同的是，在所有季节中均在中午达到峰值。大量实验研究排除了光暗条件在决定鲤鱼肠道褪黑素能系统时间模式中的直接作用，并揭示了环境非光信号作为其同步器的可能作用。基于哺乳动物的研究结果，肠道来源的褪黑素的生理意义似乎也很独特，因为其在具有旁分泌和/或自分泌功能的局部水平上的作用已得到强调。本综述的目的是总结关于肠道褪黑素的生物钟学和生理学的现有数据，并强调它们与包括鱼类在内的脊椎动物松果体中产生的同一种激素的关系。
