Improved selectivity of ZnNa3DTPA vs. Na5DTPA to abstract Cd2+ from plasma proteins in vitro

Since no chelating agent has been clinically approved for the treatment of Cd(2+) intoxicated humans, we have previously investigated diethylenetriaminepentaacetic acid (Na5DTPA) to abstract this toxic metal from plasma proteins in vitro. In addition to the complete mobilization of Cd(2+), an inadvertent abstraction of Zn(2+) from metalloproteins was also observed. Therefore, we have evaluated the effect of ZnNa3DTPA on the plasma distribution of Ca, Cd, Cu, Fe and Zn after its addition to Cd(2+)-spiked rabbit plasma. ZnNa3DTPA was as efficient as Na5DTPA in abstracting Cd(2+) (100% removal), but it did not abstract Zn(2+). Thus, complexes between essential metals (e.g. Zn(2+)) and known chelating agents emerge as feasible candidates to decrease potential adverse side effects in patients.