Reiter R J, Barlow-Walden L, Poeggeler B, Heiden S M, Clayton R J
Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284-7762, USA.
J Pineal Res. 1996 Jan;20(1):45-50. doi: 10.1111/j.1600-079x.1996.tb00238.x.
Because of the overexpression of the enzyme superoxide dismutase, individuals with Down syndrome (DS) are believed to suffer from increased oxidative stress as a result of the excessive production of oxygen-based free radicals; their exposure to higher than normal free radical production may account in part for signs of premature aging, early onset of cataracts, and of Alzheimer's disease. Free radicals are normally neutralized by free radical scavengers and other antioxidants. The pineal hormone melatonin is a potent scavenger of both the hydroxyl and peroxyl radicals, both of which are highly toxic, and a stimulator of the antioxidative enzyme glutathione peroxidase. Considering this, we deemed it important to define the day/night rhythm and levels of melatonin production in DS subjects. To do this, we assessed the urinary excretion of the chief melatonin metabolite, 6-hydroxymelatonin sulfate, throughout a 24 hr period in DS subjects; comparisons were made with the metabolite levels in the urine of non-Down siblings and parents of the DS subjects. All 8 non-Down subjects exhibited what was classified as normal urinary excretion of 6-hydroxymelatonin sulfate with the usual low daytime and high night-time levels of the melatonin metabolite. Of 12 DS subjects studied, 10 exhibited the normal day/night rhythm in urinary 6-hydroxymelatonin sulfate levels; 2 subjects were devoid of a rhythm. However, when all the data from each group were averaged, there were no noticeable differences in the absolute levels or 24 hr variations in urinary 6-hydroxymelatonin sulfate excretion between DS and non-Down subjects.
由于超氧化物歧化酶这种酶的过度表达，唐氏综合征（DS）患者被认为因氧自由基的过量产生而遭受氧化应激增加的困扰；他们暴露于高于正常水平的自由基产生可能部分解释了早衰迹象、白内障的早发以及阿尔茨海默病。自由基通常由自由基清除剂和其他抗氧化剂中和。松果体激素褪黑素是羟基自由基和过氧自由基这两种剧毒自由基的有效清除剂，也是抗氧化酶谷胱甘肽过氧化物酶的刺激剂。考虑到这一点，我们认为确定DS患者褪黑素产生的昼夜节律和水平很重要。为此，我们评估了DS患者在24小时内主要褪黑素代谢产物硫酸6-羟基褪黑素的尿排泄情况；并与非唐氏兄弟姐妹及DS患者父母尿液中的代谢产物水平进行了比较。所有8名非唐氏受试者的硫酸6-羟基褪黑素尿排泄被归类为正常，褪黑素代谢产物在白天水平较低而夜间水平较高。在研究的12名DS患者中，10名患者的硫酸6-羟基褪黑素尿水平呈现正常的昼夜节律；2名患者没有节律。然而，当对每组的所有数据进行平均时，DS患者和非唐氏受试者之间硫酸6-羟基褪黑素尿排泄的绝对水平或24小时变化没有明显差异。
