Powell J J, Burden T J, Greenfield S M, Taylor P D, Thompson R P
Gastrointestinal Laboratory, Rayne Institute, St Thomas' Hospital, London, UK.
J Inorg Biochem. 1999 Jun 30;75(3):159-65. doi: 10.1016/s0162-0134(99)00054-9.
Ethylenediaminetetraacetic acid (EDTA) is a powerful metal chelating agent used in the treatment of lead poisoning. EDTA also binds strongly to other metals. Thus, following intravenous infusion of CaNa2EDTA in healthy subjects the urinary excretion of calcium, copper, iron, magnesium and zinc were assessed. CaNa2EDTA significantly increased the urinary excretion of all metals except magnesium with greatest increases for iron (x 3.8 above baseline) and zinc (x 22). In addition, an in vitro dialysis study with a simplified serum showed that zinc (4.1 X 10(-3) mumol/h) was taken up more rapidly than iron (2.9 X 10(-3) mumol/h) by EDTA. The degree of binding of iron and zinc by EDTA depends on two factors: namely, the affinity of EDTA for Zn2+ and Fe3+, and the levels of unbound hydrated Zn2+ and Fe3+ ('free' ions). Despite differences in the rate of chelation of Zn2+ and Fe3+ by EDTA we show that the measurements of (a) circulating free iron, from routine clinical measurements of transferrin bound iron, and (b) the ratio of zinc:iron excreted in urine could provide an estimate of circulating free zinc, and thereby of zinc status, in man. In addition, EDTA treatment should be evaluated for patients with iron overload.
乙二胺四乙酸（EDTA）是一种强效金属螯合剂，用于治疗铅中毒。EDTA也能与其他金属紧密结合。因此，在健康受试者静脉输注CaNa2EDTA后，对钙、铜、铁、镁和锌的尿排泄情况进行了评估。CaNa2EDTA显著增加了除镁之外所有金属的尿排泄量，其中铁（比基线水平高3.8倍）和锌（比基线水平高22倍）的增加最为显著。此外，一项使用简化血清的体外透析研究表明，EDTA对锌（4.1×10⁻³ μmol/h）的摄取速度比对铁（2.9×10⁻³ μmol/h）的摄取速度更快。EDTA对铁和锌的结合程度取决于两个因素：即EDTA对Zn²⁺和Fe³⁺的亲和力，以及未结合的水合Zn²⁺和Fe³⁺（“游离”离子）的水平。尽管EDTA对Zn²⁺和Fe³⁺的螯合速率存在差异，但我们表明，（a）通过常规临床测量转铁蛋白结合铁来测定循环游离铁，以及（b）测定尿中锌与铁的排泄比值，可以估算人体循环游离锌，从而估算锌状态。此外，对于铁过载患者，应评估EDTA治疗效果。
