The assessment of serum nontransferrin-bound iron in chelation therapy and iron supplementation.
Nontransferrin-bound iron (NTBI) appears in the serum of individuals with iron overload and in a variety of other pathologic conditions. Because NTBI constitutes a labile form of iron, it might underlie some of the biologic damage associated with iron overload. We have developed a simple method for NTBI determination, which operates in a 96-well enzyme-linked immunosorbent assay format with sensitivity comparable to that of previous assays. A weak ligand, oxalic acid, mobilizes the NTBI and mediates its transfer to the iron chelator deferoxamine (DFO) immobilized on the plate. The amount of DFO-bound iron, originating from NTBI, is quantitatively revealed in a fluorescence plate reader by the fluorescent metallosensor calcein. No NTBI is found in normal sera because transferrin-bound iron is not detected in the assay. Thalassemic sera contained NTBI in 80% of the cases (range, 0.9-12.8 micromol/L). In patients given intravenous infusions of DFO, NTBI initially became undetectable due to the presence of DFO in the sera, but reappeared in 55% of the cases within an hour of cessation of the DFO infusion. This apparent rebound was attributable to the loss of DFO from the circulation and the possibility that a major portion of NTBI was not mobilized by DFO. NTBI was also found in patients with end-stage renal disease who were treated for anemia with intravenous iron supplements and in patients with hereditary hemochromatosis, at respective frequencies of 22% and 69%. The availability of a simple assay for monitoring NTBI could provide a useful index of iron status during chelation and supplementation treatments. (Blood. 2000;95:2975-2982)
Breuer
W
W
Department of Biological Chemistry, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel.
Ronson
A
A
Slotki
I N
IN
Abramov
A
A
Hershko
C
C
Cabantchik
Z I
ZI
D002614:Chelating Agents / Q000627:therapeutic use*; D003676:Deferoxamine / Q000627:therapeutic use*; D019587:Dietary Supplements; D016903:Drug Monitoring; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007501:Iron / Q000097:blood* / Q000627:therapeutic use*; D012010:Red-Cell Aplasia, Pure / Q000097:blood / Q000628:therapy; D014168:Transferrin / Q000378:metabolism*; D065227:Transfusion Reaction; D017086:beta-Thalassemia / Q000097:blood / Q000628:therapy*
D002614:Chelating Agents; D014168:Transferrin; D007501:Iron; D003676:Deferoxamine