Urinary excretion of essential metals following intravenous calcium disodium edetate: an estimate of free zinc and zinc status in man

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 CaNa(2)EDTA in healthy subj ects the urinary excretion of calcium, copper, iron, magnesium and zinc wer e assessed. CaNa(2)EDTA significantly increased the urinary excretion of al l metals except magnesium with greatest increases for iron (X 3.8 above bas eline) and zinc (X 22). In addition, an in vitro dialysis study with a simp lified serum showed that zinc (4.1 X 10(-3) mu mol/h) was taken up more rap idly than iron (2.9 X 10(-3) mu mol/h) by EDTA. The degree of binding of ir on and zinc by EDTA depends on two factors: namely, the affinity of EDTA fo r Zn2+ and Fe3+, and the levels of unbound hydrated Zn2+ and Fe3+ ('free' i ons). 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 c linical measurements of transferrin bound iron, and (b) the ratio of zinc:i ron excreted in urine could provide an estimate of circulating free zinc, a nd thereby of zinc status, in man. In addition, EDTA treatment should be ev aluated for patients with iron overload. (C) 1999 Elsevier Science Inc. All rights reserved.