Iron promotes cadmium binding to citrate.
Iron-cadmium interactions are important in cadmium toxicity. Dietary iron supplements may decrease cadmium retention after oral cadmium exposure but the underlying mechanism is not known. Using a CdS/AgS ion selective electrode to measure [Cd2+] in physiological saline solution at pH 7.4, we show that Fe2+ promotes Cd2+ binding to citrate thereby decreasing the availability of free Cd2+. This suggests the formation of high molecular weight Cd2+-Fe2+-citrate complexes. We confirm this suggestion by showing that 109Cd2+ is retained by 1 kDa cut off filters when present with total 50 microM Fe2+ plus 1 mM citrate but not when present with citrate alone. The formation of high molecular weight complexes may prevent Cd2+ absorption. As citrate is part of the diet, we suggest that these iron-cadmium interactions may contribute to the protective effect of iron against cadmium toxicity.
Martinez
R
R
Departments of Chemistry McMaster University, Hamilton, ON, Canada. martinez@geology.utoronto.ca
Brassard
P
P
Mwanjewe
J
J
Grover
A K
AK
D001667:Binding, Competitive; D002104:Cadmium / Q000378:metabolism*; D019343:Citric Acid / Q000378:metabolism*; D004347:Drug Interactions; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000494:pharmacology*; D007502:Iron Chelating Agents / Q000378:metabolism*; D012834:Silver / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry
D007502:Iron Chelating Agents; D013440:Sulfides; D002104:Cadmium; D019343:Citric Acid; D012834:Silver; D012965:Sodium Chloride; D007501:Iron