Transmission electron microscopic and X-ray absorption fine structure spectroscopic investigation of U repartition and speciation after accumulation in renal cells.
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.
Carrière
Marie
M
Laboratoire Pierre Süe CEA-CNRS, CEA/Saclay, 91191, Gif sur Yvette, France. marie.carriere@cea.fr
Proux
Olivier
O
Milgram
Sarah
S
Thiebault
Céline
C
Avoscan
Laure
L
Barre
Nicole
N
Den Auwer
Christophe
C
Gouget
Barbara
B
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
D017974:Uranium Compounds