Abstract
Although the kidneys comprise a critical target of uranium exposure, the dynamics of renal uranium distribution have remained obscure. Uranium is considered to function physiologically in the form of uranyl ions that have high affinity for phosphate groups. The present study applied microbeam-based elemental analysis to precisely determine the distribution of phosphorus and uranium in the kidneys of male Wistar rats exposed to uranium. One day after a single subcutaneous injection of uranyl acetate (2 mg/kg), areas of concentrated phosphorus were scattered in the S3 segments of the proximal tubule of the kidneys, whereas the S3 segments in control rats and in rats given a lower dose of uranium (0.5 mg/kg) contained phosphorus without concentrated phosphorus. Areas with concentrated phosphorus contained uranium 4- to 14-fold more than the mean uranium concentration (126–472 vs. 33.1 ± 4.6 μg/g). The chemical form of uranium in the concentrated phosphorus examined by XAFS was uranium (VI), suggesting that the interaction of uranyl ions with the phosphate groups of biomolecules could be involved in the formation of uranium concentration in the proximal tubules of kidneys in rats exposed to uranium.
Highlights
Uranium is a naturally occurring radioactive heavy metal that can cause nephrotoxicity [1,2]
We previously investigated the cellular dynamics of uranium distribution in the S3 segments of rat kidneys during acute renal toxicity using high-energy X-ray fluorescence elemental analysis with a microprobe and high-energy synchrotron radiation (SR-μXRF) [5]
Phosphorus distribution in rat kidneys was analyzed on days 1 and 3 after administration of uranyl acetate (UA) (2 mg kg−1)
Summary
Uranium is a naturally occurring radioactive heavy metal that can cause nephrotoxicity [1,2]. We previously investigated the cellular dynamics of uranium distribution in the S3 segments of rat kidneys during acute renal toxicity using high-energy X-ray fluorescence elemental analysis with a microprobe and high-energy synchrotron radiation (SR-μXRF) [5]. High-energy SR-μXRF is excellent for detecting uranium at trace levels in tissues but is not good at detection of light elements, such as phosphorus, potassium, and calcium, that can be measured using particle-induced X-ray emission with microprobe (μ-PIXE) analysis [11,12,13]. We previously reported that a single subcutaneous injection of 2 mg kg−1 (body weight) of uranyl acetate (UA) into male Wistar rats caused renal lesions in the S3 segments [14]. Colocalized phosphorus and uranium in the S3 segments was assessed using μ-PIXE and SR-μXRF, and the chemical form of the colocalized uranium in microregions was assessed by X-ray absorption fine-structure with microprobe (μXAFS)
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