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Evidence of isotopic fractionation of natural uranium in cultured human cells.

Proceedings of the National Academy of Sciences of the United States of America (2016-11-23)
Eduardo Paredes, Emilie Avazeri, Véronique Malard, Claude Vidaud, Pascal E Reiller, Richard Ortega, Anthony Nonell, Hélène Isnard, Frédéric Chartier, Carole Bresson
ABSTRACT

The study of the isotopic fractionation of endogen elements and toxic heavy metals in living organisms for biomedical applications, and for metabolic and toxicological studies, is a cutting-edge research topic. This paper shows that human neuroblastoma cells incorporated small amounts of uranium (U) after exposure to 10 µM natural U, with preferential uptake of the 235U isotope with regard to 238U. Efforts were made to develop and then validate a procedure for highly accurate n(238U)/n(235U) determinations in microsamples of cells. We found that intracellular U is enriched in 235U by 0.38 ± 0.13‰ (2σ, n = 7) relative to the exposure solutions. These in vitro experiments provide clues for the identification of biological processes responsible for uranium isotopic fractionation and link them to potential U incorporation pathways into neuronal cells. Suggested incorporation processes are a kinetically controlled process, such as facilitated transmembrane diffusion, and the uptake through a high-affinity uranium transport protein involving the modification of the uranyl (UO22+) coordination sphere. These findings open perspectives on the use of isotopic fractionation of metals in cellular models, offering a probe to track uptake/transport pathways and to help decipher associated cellular metabolic processes.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Phorbol 12-myristate 13-acetate, ≥99% (TLC), film or powder
Sigma-Aldrich
Tris(2-pyridylmethyl)amine, 98%