Renal localization and quantification of uranium in rodent exposed to uranyl nitrate by LA-ICP-MS

International audienceThe over-exposure to uranium results in renal toxicity, which is derived form an excessive accumulation of the element in the kidney, characterized by reduced glomerular filtration, exerting its toxic effect by chemical and radiological action [1-3]. In addition, its tissue distribution is heterogeneous mostly accumulating and producing pathological lesions in the S2 and S3 segments of the proximal tubule located in the cortical zone (100-fold above mean renal concentration) [4-6]. Chronic exposure (occupational exposure) to uranium, is linked to its bioaccumulation in kidney and could be associated with renal dysfunction, an increased risk of cancer mortality and kidney failure [7-9]. Up to day, few quantitative studies have been carried out employing high-energy synchrotron radiation X-ray fluorescence analysis (SR-XRF) and X-ray absorption fine structure (XAFS) [10, 11]. Unfortunately, the limited access to these analytical techniques limits considerably its daily use for routine analysis. Therefore, this works presents the development of an analytical methodology based on mass spectrometry imaging (MSI) using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for mapping and quantifying uranium in histological tissue sections of mouse kidney. To the author’s knowledge a single work has been published recently for the semi-quantitative analysis of uranium in mice kidneys due to the lack of an appropriate internal standard [12]. In this study, the uranium exposure of mice was performed using a direct nasal instillation of few µL of uranyl nitrate solutions at different uranium concentrations. Total uranium analysis was done by conventional liquid ICP-MS after acid digestion using one kidney from each pair. In parallel, the other kidney was employed for LA-ICP-MS analysis. In order to perform quantitative LA-ICPMS bio-imaging analysis, synthetic matrix-matched laboratory standards and a normalisation strategy based on internal standard spiked gelatine were developed. Preliminary quantitative images of cryo-sections revealed heterogeneous distribution of uranium within the renal tissue, being the cortical concentration 60-fold higher than the medullary concentration