文摘
Uranium (U), as a heavy metal, is a strong chemical toxicant, which induces the damage to proximaltubule kidney cells. In order to reproduce U toxicity in vitro and to avoid precipitation, it is necessaryto complex it with a strong ligand such as bicarbonate before dilution with cell culture medium. It wasrecently shown, in vitro on the NRK-52E normal renal tubular epithelial cells, that citrate increased thetoxicity of U(VI)-bicarbonate complexes. This property was attributed to a change in U speciation,characterized by the occurrence of U(VI)-citrate complexes, which were supposed to be more toxicthan U(VI)-bicarbonate. Here, we present the results of extended X-ray absorption fine structurespectroscopy (EXAFS) analyses of the media that were used to expose cells in vitro. Resulting datashow that even when citrate is added to the exposure medium, the predominant species is U(VI)-bicarbonate. Nonetheless, citrate increases U(VI) toxicity and accelerates its intracellular accumulationkinetics, without inducing precipitation. This study emphasizes another parameter that modulates U(VI)toxicity for renal tubule cells and further characterizes the mechanisms of U(VI) toxicity.