title: Transmission electron microscopic and X-ray absorption fine structure spectroscopic investigation of U repartition and speciation after accumulation in renal cells.
abstract: After environmental contamination, U accumulates in the kidneys and in bones, where it causes visible damage. Recent in vitro data prove that the occurrence of citrate increases U bioavailability without changing its speciation. Two hypotheses can explain the role of citrate: it either modifies the U intracellular metabolization pathway, or it acts on the transport of U through cell membrane. To understand which mechanisms lead to increased bioavailability, we studied the speciation of U after accumulation in NRK-52E kidney cells. U speciation was first identified in various exposure media, containing citrate or not, in which U was supplied as U carbonate. The influence of serum proteins was analyzed in order to detect the formation of macromolecular complexes of U. Transmission electron microscopy (TEM) was employed to follow the evolution of the U species distribution among precipitated and soluble forms. Finally, extended X-ray absorption fine structure spectroscopy (EXAFS) enabled the precipitates observed to be identified as U-phosphate. It also demonstrated that the intracellular soluble form of U is U carbonate. These results suggest that citrate does not change U metabolization but rather plays a role in the intracellular accumulation pathway. U speciation inside cells was directly and clearly identified for the first time. These results elucidate the role of U speciation in terms of its bioavailability and consequent health effects.
authors.affiliation: Laboratoire Pierre Süe CEA-CNRS, CEA/Saclay, 91191, Gif sur Yvette, France. marie.carriere@cea.fr
authors.forename: Marie
authors.initials: M
authors.lastname: Carrière
authors.forename: Olivier
authors.initials: O
authors.lastname: Proux
authors.forename: Sarah
authors.initials: S
authors.lastname: Milgram
authors.forename: Céline
authors.initials: C
authors.lastname: Thiebault
authors.forename: Laure
authors.initials: L
authors.lastname: Avoscan
authors.forename: Nicole
authors.initials: N
authors.lastname: Barre
authors.forename: Christophe
authors.initials: C
authors.lastname: Den Auwer
authors.forename: Barbara
authors.initials: B
authors.lastname: Gouget
mesh_terms: D000818:Animals; D016923:Cell Death / Q000187:drug effects; D007668:Kidney / Q000378:metabolism* / Q000648:ultrastructure; D018374:LLC-PK1 Cells; D046529:Microscopy, Electron, Transmission; D051381:Rats; D013057:Spectrum Analysis; D013552:Swine; D017974:Uranium Compounds / Q000378:metabolism* / Q000493:pharmacokinetics; D014965:X-Rays
chemical_list: D017974:Uranium Compounds