Iron promotes cadmium binding to citrate

Iron-cadmium interactions are important in cadmium toxicity. Dietary iron s upplements may decrease cadmium retention after oral cadmium exposure but t he underlying mechanism is not known. Using a CdS/AgS ion selective electro de to measure [Cd2+] in physiological saline solution at pH 7.4, we show th at Fe2+ promotes Cd2+ binding to citrate thereby decreasing the availabilit y of free Cd2+. This suggests the formation of high molecular weight Cd2+-F e2+-citrate complexes. We confirm this suggestion by showing that Cd-109(2) is retained by 1 kDa cut off filters when present with total 50 muM Fe-2 plus 1 mM citrate but not when present with citrate alone. The formation o f high molecular weight complexes may prevent Cd2+ absorption. As citrate i s part of the diet, we suggest that these iron-cadmium interactions may con tribute to the protective effect of iron against cadmium toxicity.