Chan S, Gerson B, Subramaniam S
Quest Diagnostics Incorporated Nichols Institute, San Juan Capistrano, California, USA.
Clin Lab Med. 1998 Dec;18(4):673-85.
Copper, zinc, selenium, and molybdenum are involved in many biochemical processes supporting life. The most important of these processes are cellular respiration, cellular utilization of oxygen, DNA and RNA reproduction, maintenance of cell membrane integrity, and sequestration of free radicals. Copper, zinc, and selenium are involved in destruction of free radicals through cascading enzyme systems. Superoxide radicals are reduced to hydrogen peroxide by superoxide dismutases in the presence of copper and zinc cofactors. Hydrogen peroxide is then reduced to water by the selenium-glutathione peroxidase couple. Efficient removal of these superoxide free radicals maintains the integrity of membranes, reduces the risk of cancer, and slows the aging process. On the other hand, excess intake of these trace elements leads to disease and toxicity; therefore, a fine balance is essential for health. Trace element--deficient patients usually present with common symptoms such as malaise, loss of appetite, anemia, infection, skin lesions, and low-grade neuropathy, thus complicating the diagnosis. Symptoms for intoxication by trace elements are general, for example, flu-like and CNS symptoms, fever, coughing, nausea, vomiting, diarrhea, anemia, and neuropathy. A combination of observation, medical and dietary history, and analyses for multiple trace elements is needed to pinpoint the trace element(s) involved. Serum, plasma, and erythrocytes may be used for the evaluation of copper and zinc status, whereas only serum or plasma is recommended for selenium. Whole blood is preferred for molybdenum. When trace element levels are inconsistent with medical evaluations, a test for activity of the suspected enzyme(s) would support the differential diagnosis. Furthermore, it is important to differentiate whether trace element deficiency or toxicity is the primary cause of the disorder, or is secondary to other underlying diseases. Only successful treatment of the primary disorder will lead to complete recovery. In the event of sample contamination during collection or analysis, the physician may be misled by falsely elevated results. Royal blue top evacuated tubes containing negligibly low concentrations of the trace element or acid-washed plastic sterilized syringes should be used for blood, serum, or plasma collection. Powdered gloves must be avoided. When possible, mineral supplements are not to be administered to the patient for a minimum of 3 days prior to sample collection. Serum and plasma specimens are to be transported in acid-washed polypropylene and polyethylene tubes. Analysis is performed in a controlled environment to minimize or eliminate contamination. During analysis, all laboratory wares should be acid-washed for decontamination. A detailed description of these precautions may be found in reviews by Aitio and Jarvisalo and by Chan and Gerson. Copper and zinc analysis on serum and plasma are commonly performed by flame atomic absorption spectrometry, inductively coupled plasma-atomic emission spectrometry, and inductively coupled plasma-mass spectrometry. Serum and plasma selenium levels are determined by graphite furnace atomic absorption with Zeeman background correction and neutron activation analysis. Molybdenum levels are best determined by neutron activation and highly sensitive inductively coupled plasma-mass spectrometry. The reader is referred to reviews by Tsalev and Jarvis.
铜、锌、硒和钼参与许多维持生命的生化过程。这些过程中最重要的是细胞呼吸、细胞对氧气的利用、DNA和RNA的复制、细胞膜完整性的维持以及自由基的清除。铜、锌和硒通过级联酶系统参与自由基的清除。在铜和锌辅因子存在的情况下，超氧化物歧化酶将超氧自由基还原为过氧化氢。然后，硒-谷胱甘肽过氧化物酶将过氧化氢还原为水。有效清除这些超氧自由基可维持膜的完整性，降低患癌风险，并减缓衰老过程。另一方面，过量摄入这些微量元素会导致疾病和毒性；因此，保持微妙的平衡对健康至关重要。微量元素缺乏的患者通常会出现诸如不适、食欲不振、贫血、感染、皮肤病变和轻度神经病变等常见症状，从而使诊断变得复杂。微量元素中毒的症状较为普遍，例如类似流感和中枢神经系统的症状、发热、咳嗽、恶心、呕吐、腹泻、贫血和神经病变。需要结合观察、病史和饮食史以及多种微量元素分析来确定所涉及的微量元素。血清、血浆和红细胞可用于评估铜和锌的状态，而对于硒，仅推荐使用血清或血浆。钼的检测首选全血。当微量元素水平与医学评估结果不一致时，对可疑酶活性的检测将有助于鉴别诊断。此外，区分微量元素缺乏或毒性是疾病的主要原因还是继发于其他潜在疾病很重要。只有成功治疗原发性疾病才能实现完全康复。如果在采集或分析过程中样本受到污染，医生可能会被错误升高的结果误导。采集血液、血清或血浆时应使用含微量元素浓度极低的皇家蓝顶真空采血管或酸洗过的塑料无菌注射器。必须避免使用粉末手套。尽可能在采集样本前至少3天不给患者服用矿物质补充剂。血清和血浆标本应在酸洗过的聚丙烯和聚乙烯管中运输。分析在受控环境中进行，以尽量减少或消除污染。分析过程中，所有实验室器具都应进行酸洗以进行去污。这些预防措施的详细描述可在艾蒂奥和贾维萨洛以及陈和格森的综述中找到。血清和血浆中铜和锌的分析通常采用火焰原子吸收光谱法、电感耦合等离子体原子发射光谱法和电感耦合等离子体质谱法。血清和血浆硒水平通过带塞曼背景校正的石墨炉原子吸收法和中子活化分析法测定。钼水平最好通过中子活化法和高灵敏度电感耦合等离子体质谱法测定。读者可参考察列夫和贾尔维斯的综述。
