Accumulation and Distribution of Uranium in Rats after Implantation with Depleted Uranium Fragments

Purpose: The aim of our study was to clarify the accumulation and distribution of uranium in depleted uranium (DU) implanted rats. Materials and Methods: Male Sprague-Dawley rats were surgically implanted in gastrocnemius muscle with DU fragments at 3 dose levels (low, medium and high), and biologically inert tantalum (Ta) fragments were used as controls. At 1 day and 7, 30, 90, 180 and 360 days after implantation, the rats were euthanized and tissue samples including serum and urine were collected to analyze the uranium levels by inductively coupled plasma-mass spectrometry (ICP-MS). Results: At all time points, uranium levels in all the DU implanted groups were higher than that in Ta control group, and uranium concentrations in kidney and bone were significantly greater than that in other tissues. Otherwise, uranium concentrations increased with a close correlation to the implanted DU doses and duration of exposure, with a peak at 90 days post-implantation, after which followed by a decreasing period, but still maintained at a relatively high level even at 360 days post- implantation. The uranium concentrations in bone were 6.92 ± 0.97 μg U/g, 16.35 ± 1.67 μg U/g and 21.64 ± 3.68 μg U/g in the low-, medium- and high-dose group animals, while values in kidney tissues were 10.66 ± 1.10 μg U/g, 14.06 ± 1.28 μg U/g and 17.79 ± 2.87 μg U/g, respectively, at 360 days post-implantation. Conclusion: It was concluded that kidney and bone are the primary reservoirs for uranium redistributed from intramuscularly embedded fragments, and the accumulations in kidney, bone and many other tissues suggest the potential for unanticipated physiological consequences of chronic exposure to DU.