Abstract
Tungsten accumulates in bone but is neither labile nor inert once absorbed. Tungsten’s relatively high cytosolic solubility and availability are problematic given its association with childhood lymphocytic leukemia. In light of tungsten’s technological prevalence, and the increased concern of regulatory agencies, here we characterize the chemical form and localization in mice exposed to tungsten through drinking water. Using X-ray fluorescence spectroscopy, we report accumulation of tungsten in bone tissue with some sites having ~10-fold greater intensities than background levels. The long bone tissue studied includes cortical, cancellous and bone marrow. Persistence of tungsten in cortical bone tissue following removal of the source indicates that it is retained in an insoluble form. The X-ray absorption near-edge structure spectra for tungsten in these tissues indicate that it is no longer in the originally administered form, orthotungstate, but rather resembles the heteropolytungsate species, phosphotungstate.
Highlights
Tungsten accumulates in bone but is neither labile nor inert once absorbed
SR-μXRF is a nondestructive technique that has been applied in diverse fields including archeology, forensics, anthropology, and geology to simultaneously identify and spatially resolve multiple trace elements ranging from the macroscopic to microscopic scale[6]
The localized distribution of tungsten throughout all the main components of long bone tissue for mice exposed to 1000 ppm tungsten via sodium tungstate (Na2WO4) in drinking water over the course of 1, 4, and 12 weeks was determined using SR-μXRF
Summary
Tungsten accumulates in bone but is neither labile nor inert once absorbed. Tungsten’s relatively high cytosolic solubility and availability are problematic given its association with childhood lymphocytic leukemia. Other bone-accumulating metals, such as lead and strontium[6], substitute for calcium in hydroxyapatite, the calcium-phosphate matrix of bone, and can be removed using standard chelation therapy[7] This treatment, is ineffective at removing anionic oxometallate anions of tungsten, which is retained in cortical bone tissue even after the source is removed[3,8]. This suggests alternate speciation or accumulation mechanisms for tungsten compared to other metals. We use synchrotron radiation micro X-ray fluorescence (SR-μXRF) spectroscopy and micro X-ray absorption near-edge structure (SR-μXANES) spectroscopy to show that tungsten is heterogeneously distributed in bone tissue and that the in vivo speciation of tungsten is in the form of in situ generated polytungstes
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