The evolution of depleted uranium as an environmental risk factor: lessons from other metals

Enhanced uranium sequestration through selenite-modified nano-chitosan loaded with melatonin: Facilitating U(IV) conversion

The combined chemotoxicity and radiotoxicity associated with uranium, utilized in nuclear industry and military applications, poses significant threats to human health. Among uranium pollutants, uranyl is particularly concerning due to its high absorptivity and potent nephrotoxicity in its + 6 valence state. Here, we have serendipitously found Na2SeO3 facilitates the conversion of U(VI) to U(IV) precipitates. A novel approach involving nano-chitosan loaded internally with melatonin and externally modified with selenite (NPs Cs-Se/MEL) was introduced. This modification not only enhances the conversion of U(VI) to U(IV) but also preserves the spherical nanostructure and specific surface area, leading to increased adsorption of U(VI) compared to unmodified samples. Selenite modification improves lysosomal delivery in HEK-293 T cells and kidney distribution of the nanoparticles. Furthermore, NPs Cs-Se/MEL demonstrated a heightened uranium concentration in urine and exhibited remarkable efficiency in uranium removal, resulting in a reduction of uranium deposition in serum, kidneys, and femurs by up to 52.02 %, 46.79 %, and 71.04 %, respectively. Importantly, NPs Cs-Se/MEL can be excreted directly from the kidneys into urine when carrying uranium. The results presented a novel mechanism for uranium adsorption, making selenium-containing nano-materials attractive for uranium sequestration and detoxification.

Depleted uranium induces thyroid damage through activation of ER stress via the thrombospondin 1-PERK pathway

Depleted uranium (DU) can cause damage to the body, but its effects on the thyroid are unclear. The purpose of this study was to investigate the DU-induced thyroid damage and its potential mechanism in order to find new targets for detoxification after DU poisoning. A model of acute exposure to DU was constructed in rats. It was observed that DU accumulated in the thyroid, induced thyroid structure disorder and cell apoptosis, and decreased the serum T4 and FT4 levels. Gene screening showed that thrombospondin 1 (TSP-1) was a sensitive gene of DU, and the expression of TSP-1 decreased with the increase of DU exposure dose and time. TSP-1 knockout mice exposed to DU had more severe thyroid damage and lower serum FT4 and T4 levels than wild-type mice. Inhibiting the expression of TSP-1 in FRTL-5 cells aggravated DU-induced apoptosis, while exogenous TSP-1 protein alleviated the decreased viability in FRTL-5 cells caused by DU. It was suggested that DU may caused thyroid damage by down-regulating TSP-1. It was also found that DU increased the expressions of PERK, CHOP, and Caspase-3, and 4-Phenylbutyric (4-PBA) alleviated the DU-induced FRTL-5 cell viability decline and the decrease levels of rat serum FT4 and T4 caused by DU. After DU exposure, the PERK expression was further up-regulated in TSP-1 knockout mice, and the increased expression of PERK was alleviated in TSP-1 over-expressed cells, as well as the increased expression of CHOP and Caspase-3. Further verification showed that inhibition of PERK expression could reduce the DU-induced increased expression of CHOP and Caspase-3. These findings shed light on the mechanism that DU may activate ER stress via the TSP 1-PERK pathway, thereby leading to thyroid damage, and suggest that TSP-1 may be a potential therapeutic target for DU-induced thyroid damage.

Horizontal and Vertical Transport of Uranium in an Arid Weapon-Tested Ecosystem

Armor-penetrating projectiles and fragments of depleted uranium (DU) have been deposited in soils at weapon-tested sites. Soil samples from these military facilities were analyzed by inductively coupled plasma-optical emission spectroscopy and X-ray diffraction to determine U concentrations and transport across an arid ecosystem. Under arid conditions, both vertical transport driven by evaporation (upward) and leaching (downward) and horizontal transport of U driven by surface runoff in the summer were observed. Upward vertical transport was simulated and confirmed under laboratory-controlled conditions, to be leading to the surface due to capillary action via evaporation during alternating wetting and drying conditions. In the field, the 92.8% of U from DU penetrators and fragments remained in the top 5 cm of soil and decreased to background concentrations in less than 20 cm. In locations prone to high amounts of water runoff, U concentrations were reduced significantly after 20 m from the source due to high surface runoff. Uranium was also transported throughout the ecosystem via plant uptake and wild animal consumption between trophic levels, but with limited accumulation in edible portions in plants and animals.

Mortality experience of US veterans following service as international peacekeepers in Bosnia/Kosovo theater, 1996-2002

BACKGROUND

Beginning in 1996 US military personnel served as peacekeeping forces in Bosnia/Kosovo. No studies have assessed the long-term post-deployment health of this US cohort. Based on the health concerns raised in studies of military personnel from other countries, this study focused on mortality due to Leukemia, respiratory disease, respiratory cancer, and heart disease.

METHODS

This study compared the post-war cause-specific mortality of 53,320 veterans who deployed to Bosnia/Kosovo between 1996-2002 to that of 117,267 veterans who also served in the military between 1996-2002, but were not deployed to Bosnia/Kosovo. Expressed as standardized mortality ratios (SMR)s the cause-specific mortality for both deployed and non-deployed were compared separately to that of the US general population. Cause-specific mortality risks among Bosnia/Kosovo veterans relative to that of non-deployed veterans were assessed using Hazard Ratios (HR)s generated by Cox proportional-hazards models.

RESULTS

The overall mortality of both deployed and non-deployed veterans was almost half that of the US population, SMR = 0.59, 95%, C.I., 0.55-0.62 and SMR = 0.66, 95%, C.I., 0.64-0.68, respectively. Neither group of veterans had any excess of disease related mortality compared to that of the US population. Compared to non-deployed, deployed veterans did not experience any increased risks for any of the diseases of a priori interest.

CONCLUSION

It does not appear that US military deployed to Bosnia/Kosovo have any increased risks of disease related mortality. However, this study would not have been able to detect increased risk of cancers with latency periods that exceeded the 18 years of follow-up available in this study.

Passive, non-intrusive assay of depleted uranium

The ability to detect neutrons from the spontaneous fission of ²³⁸U in samples of depleted uranium with organic liquid scintillation detectors is presented. In this paper we introduce a small modular organic liquid scintillator detector array that can detect changes in mass of ²³⁸U between 3.69 g and 14.46 g. To do this, 18-h assays of various masses of 0.3% wt. of depleted uranium dioxide were assessed using four EJ-309 detectors, a mixed field analyser operated in pulse gradient analysis mode, and associated counting components. We observe a background-corrected fast neutron count sensitivity of (2.0 ± 0.3) × 10^-4 n g^-1 s^-1 per detector. This research demonstrates a proof of concept for depleted uranium quantity to be assessed passively on a non-intrusive basis via its spontaneous fission decay.

Uranyl Functionalization Mediated by Redox-Active Ligands: Generation of O-C Bonds via Acylation

A series of uranyl compounds with the redox-active iminoquinone ligand have been synthesized, and their electronic structures elucidated using multinuclear NMR, EPR, electronic absorption spectroscopies, SQUID magnetometry, and X-ray crystallography. Characterization and analysis of the iminoquinone (iq⁰) complex, (^dippiq)UO₂(OTf)₂THF (1-iq), the iminosemiquinone (isq^1-) complex, (^dippisq)₂UO₂THF (2-isq), and the amidophenolate (ap^2-) complex, [(^dippap)₂UO₂THF][K(18-crown-6)(THF)₂]₂(3-ap crown) show that reduction events are ligand-based, with the uranium center remaining in the hexavalent state. Reactivity of 2-isq with B-chlorocatecholborane or pivaloyl chloride leads to U-O_uranyl bond scission and reduction of U(VI) to U(IV) concomitant with ligand oxidation along with organic byproducts. ¹⁸O isotopic labeling experiments along with IR spectroscopy, mass spectrometry, and multinuclear NMR spectroscopy confirm that the organic byproducts contain oxygen atoms which originate from U-O_uranyl bond activation.

A Review on Toxicodynamics of Depleted Uranium

Depleted uranium (DU) is an important by product in uranium enrichment process. Due to its applications in civilian and also military activity, DU emerged as environmental pollutant. The exposure to DU can occur via external or internal pathways. In external exposure, mainly beta radiation from the decay products contributes to DU toxicity. Internal exposure to DU is more important and can occur through ingestion of DU-contaminated water and food and inhalation of DU aerosols. There is limited information about health effects and mechanism of DU after environmental exposure. Kidney is reported as the main target organ for the chemical toxicity of this metal that was reported in Persian Gulf syndrome. Alterations in behavior, some neurologic adverse effects, immunotoxicity, embryo-toxicity and hepatotoxicity were observed in chronic exposure to DU. Also, the increased risk of cancer was revealed in epidemiological and experimental studies. Several mechanisms were suggested for DU toxicity such as oxidative stress, mitochondrial toxicity and inflammation. In fact, uranium like other toxic heavy metals can induce oxidative damage and apoptosis via mitochondrial pathway and inflammatory response. In this review, we have discussed the kinetic of DU including source and exposure pathway. In addition, the health effects of DU and also its toxic mechanism have been highlighted.

Meta-analysis of depleted uranium levels in the Middle East region

Since the first widespread use of depleted uranium in military in the 1991 Gulf War, the so-called "Gulf War Syndrome" has been a topic of ongoing debate. However, a low number of reliable scientific papers demonstrating the extent of possible contamination as well as its connection to the health status of residents and deployed veterans has been published. The authors of this study have therefore aimed to make a selection of data based on strict inclusion and exclusion criteria. With the goal of clarifying the extent of DU contamination after the Gulf Wars, previously published data regarding the levels of DU in the Middle East region were analyzed and presented in the form of a meta-analysis. In addition, the authors attempted to make a correlation between the DU levels and their possible effects on afflicted populations. According to results observed by comparing ²³⁴U/²³⁸U and ²³⁵U/²³⁸U isotopic activity ratios, as well as ²³⁵U/²³⁸U mass ratios in air, water, soil and food samples among the countries in the Middle East region, areas indicating contamination with DU were Al Doha, Manageesh and Um Al Kwaty in Kuwait, Al-Salman, Al-Nukhaib and Karbala in Iraq, Beirut in Lebanon and Sinai in Egypt. According to these data, no DU contamination was observed in Algeria, Israel, Afghanistan, Oman, Qatar, Iran, and Yemen. Due to the limited number of reliable data on the health status of afflicted populations, it was not possible to make a correlation between DU levels and health effects in the Middle East region.

Chronic Exposure to Uranium from Gestation: Effects on Behavior and Neurogenesis in Adulthood

Uranium exposure leads to cerebral dysfunction involving for instance biochemical, neurochemical and neurobehavioral effects. Most studies have focused on mechanisms in uranium-exposed adult animals. However, recent data on developing animals have shown that the developing brain is also sensitive to uranium. Models of uranium exposure during brain development highlight the need to improve our understanding of the effects of uranium. In a model in which uranium exposure began from the first day of gestation, we studied the neurobehavioral consequences as well as the progression of hippocampal neurogenesis in animals from dams exposed to uranium. Our results show that 2-month-old rats exposed to uranium from gestational day 1 displayed deficits in special memory and a prominent depressive-like phenotype. Cell proliferation was not disturbed in these animals, as shown by 5-bromo-2′deoxyuridine (BrdU)/neuronal specific nuclear protein (NeuN) immunostaining in the dentate gyrus. However, in some animals, the pyramidal cell layer was dispersed in the CA3 region. From our previous results with the same model, the hypothesis of alterations of neurogenesis at prior stages of development is worth considering, but is probably not the only one. Therefore, further investigations are needed to correlate cerebral dysfunction and its underlying mechanistic pathways.

Mortality in Italian veterans deployed in Bosnia-Herzegovina and Kosovo

BACKGROUND AND AIMS

The possible increase of cancer risk in military personnel deployed in Balkans during and after the 1992-1999 wars, mainly related to the depleted uranium, was addressed by several studies on European veterans of those war theatres. This article reports on the results of the mortality study on the Italian cohort of Bosnia and Kosovo veterans (Balkan cohort).

METHODS

Mortality rates for the Balkan cohort (71 144 persons) were compared with those of the Italian general population as well as to those of a comparable and unselected control cohort of not deployed military personnel (114 269 persons). Ascertainment of vital status during the period 1995-2008 of all the persons in the two cohorts has been carried out through deterministic record linkage with the national death records database, from information provided by the respective Armed Force General Staff, and through the civil registry offices of the veterans' residence or birth municipalities.

RESULTS

The Balkan cohort experienced a mortality rates lower than both the general population (SMR = 0.56; 95% CI 0.51-0.62) and the control group (SMR = 0.88; 95% CI 0.79-0.97). Cancer mortality in the deployed cohort group was half of that from the general population mortality rates (SMR = 0.50; 95% CI 0.40-0.62) and slightly lower if compared with the control group cancer mortality rates (SMR = 0.95; 95% CI 0.77-1.18).

CONCLUSION

Balkan veteran cohort did not show any increase in general mortality or in cancer mortality.

Environmental assessment of depleted uranium used in military armor-piercing rounds in terrestrial systems

Depleted uranium (DU) from the military testing and use of armor-piercing kinetic energy penetrators has been shown to accumulate in soils; however, little is known about the toxicity of DU geochemical species created through corrosion or weathering. The purpose of the present study was to assess the toxic effects and bioaccumulation potential of field-collected DU oxides to the model terrestrial invertebrates Eisenia fetida (earthworm) and Porcellio scaber (isopod). Earthworm studies were acute (72 h) dermal exposures or 28-d spiked soil exposures that used noncontaminated field-collected soils from the US Army's Yuma and Aberdeen Proving Grounds. Endpoints assessed in earthworm testing included bioaccumulation, growth, reproduction, behavior (soil avoidance), and cellular stress (neutral red uptake in coelomocytes). Isopod testing used spiked food, and endpoints assessed included bioaccumulation, survival, and feeding behavior. Concentration-dependent bioaccumulation of DU in earthworms was observed with a maximum bioaccumulation factor of 0.35; however, no significant reductions in survival or impacts to cellular stress were observed. Reproduction lowest-observed-effect concentrations (LOEC) of 158 mg/kg and 96 mg/kg were observed in Yuma Proving Ground and a Mississippi reference soil (Karnac Ferry), respectively. Earthworm avoidance of contaminated soils was not observed in 48-h soil avoidance studies; however, isopods were shown to avoid food spiked with 12.7% by weight DU oxides through digital tracking studies.

Depleted uranium instead of lead in munitions: the lesser evil

Uranium has many similarities to lead in its exposure mechanisms, metabolism and target organs. However, lead is more toxic, which is reflected in the threshold limit values. The main potential hazard associated with depleted uranium is inhalation of the aerosols created when a projectile hits an armoured target. A person can be exposed to lead in similar ways. Accidental dangerous exposures can result from contact with both substances. Encountering uranium fragments is of minor significance because of the low penetration depth of alpha particles emitted by uranium: they are unable to penetrate even the superficial keratin layer of human skin. An additional cancer risk attributable to the uranium exposure might be significant only in case of prolonged contact of the contaminant with susceptible tissues. Lead intoxication can be observed in the wounded, in workers manufacturing munitions etc; moreover, lead has been documented to have a negative impact on the intellectual function of children at very low blood concentrations. It is concluded on the basis of the literature overview that replacement of lead by depleted uranium in munitions would be environmentally beneficial or largely insignificant because both lead and uranium are present in the environment.

Microanalytical X-ray imaging of depleted uranium speciation in environmentally aged munitions residues

Use of depleted uranium (DU) munitions has resulted in contamination of the near-surface environment with penetrator residues. Uncertainty in the long-term environmental fate of particles produced by impact of DU penetrators with hard targets is a specific concern. In this study DU particles produced in this way and exposed to the surface terrestrial environment for longer than 30 years at a U.K. firing range were characterized using synchrotron X-ray chemical imaging. Two sites were sampled: a surface soil and a disposal area for DU-contaminated wood, and the U speciation was different between the two areas. Surface soil particles showed little extent of alteration, with U speciated as oxides U3O7 and U3O8. Uranium oxidation state and crystalline phase mapping revealed these oxides occur as separate particles, reflecting heterogeneous formation conditions. Particles recovered from the disposal area were substantially weathered, and U(VI) phosphate phases such as meta-ankoleite (K(UO2)(PO4) · 3H2O) were dominant. Chemical imaging revealed domains of contrasting U oxidation state linked to the presence of both U3O7 and meta-ankoleite, indicating growth of a particle alteration layer. This study demonstrates that substantial alteration of DU residues can occur, which directly influences the health and environmental hazards posed by this contamination.

Remediation of soils contaminated with particulate depleted uranium by multi stage chemical extraction

Contamination of soils with depleted uranium (DU) from munitions firing occurs in conflict zones and at test firing sites. This study reports the development of a chemical extraction methodology for remediation of soils contaminated with particulate DU. Uranium phases in soils from two sites at a UK firing range, MOD Eskmeals, were characterised by electron microscopy and sequential extraction. Uranium rich particles with characteristic spherical morphologies were observed in soils, consistent with other instances of DU munitions contamination. Batch extraction efficiencies for aqueous ammonium bicarbonate (42-50% total DU extracted), citric acid (30-42% total DU) and sulphuric acid (13-19% total DU) were evaluated. Characterisation of residues from bicarbonate-treated soils by synchrotron microfocus X-ray diffraction and X-ray absorption spectroscopy revealed partially leached U(IV)-oxide particles and some secondary uranyl-carbonate phases. Based on these data, a multi-stage extraction scheme was developed utilising leaching in ammonium bicarbonate followed by citric acid to dissolve secondary carbonate species. Site specific U extraction was improved to 68-87% total U by the application of this methodology, potentially providing a route to efficient DU decontamination using low cost, environmentally compatible reagents.

Exposure to depleted uranium does not alter the co-expression of HER-2/neu and p53 in breast cancer patients

Background

Amongst the extensive literature on immunohistochemical profile of breast cancer, very little is found on populations exposed to a potential risk factor such as depleted uranium. This study looked at the immunohistochemical expression of HER-2/neu (c-erbB2) and p53 in different histological types of breast cancer found in the middle Euphrates region of Iraq, where the population has been exposed to high levels of depleted uranium.

Findings

The present investigation was performed over a period starting from September 2008 to April 2009. Formalin-fixed, paraffin-embedded blocks from 70 patients with breast cancer (62 ductal and 8 lobular carcinoma) were included in this study. A group of 25 patients with fibroadenoma was included as a comparative group, and 20 samples of normal breast tissue sections were used as controls. Labeled streptavidin-biotin (LSAB+) complex method was employed for immunohistochemical detection of HER-2/neu and p53.

The detection rate of HER-2/neu and p53 immunohistochemical expression were 47.14% and 35.71% respectively in malignant tumors; expression was negative in the comparative and control groups (p < 0.05).

HER-2/neu immunostaining was significantly associated with histological type, tumor size, nodal involvement, and recurrence of breast carcinoma (p < 0.05), p53 immunostaining was significantly associated with tumor size, nodal involvement and recurrence of breast cancer (p < 0.05). There was greater immunoexpression of HER-2/neu in breast cancer in this population, compared with findings in other populations.

Both biomarkers were positively correlated with each other. Furthermore, all the cases that co-expressed both HER-2/neu and p53 showed the most unfavorable biopathological profile.

Conclusion

P53 and HER-2/neu over-expression play an important role in pathogenesis of breast carcinoma. The findings indicate that in regions exposed to high levels of depleted uranium, although p53 and HER-2/neu overexpression are both high, correlation of their expression with age, grade, tumor size, recurrence and lymph node involvement is similar to studies that have been conducted on populations not exposed to depleted uranium. HER-2/neu expression in breast cancer was higher in this population, compared with results on non-exposed populations.

Effects of uranium depletion on 1α-hydroxylase in kidney of rats

This study was designed to evaluate the effects of depleted uranium (DU) on 1α-hydroxylase in the kidney of rats and to delinerate the mechanism of damage to kidneys and bones by DU. Male Sprague-Dawley rats were surgically implanted with DU fragments at three dose levels (0.1 g, 0.2 g and 0.3 g). After 3, 6 or 12 months, the concentration of 1α,25(OH)2D3 in the kidney was measured by radioimmunoassay. The activity of 1α-hydroxylase was shown by the production of 1α,25(OH)2D3 after incubation. The results showed that the 1α-hydroxylase activity in the kidney was decreased after 3 months (27.2% at the medium dose DU group, p < 0.05; 33.4% at the high dose DU group, p < 0.01). In contrast, at 6 months and 12 months after implantation of DU, the activity of renal 1α-hydroxylase in DU-treated animals was not decreased significantly in comparison with the controls (p > 0.05). On the other hand, the activity of renal 1α-hydroxylase was decreased by 33.1% (p < 0.05) and 34.4% (p < 0.01) in blank control groups at 6 and 12 months, respectively, when compared with the blank control group at 3 months. In conclusion, this study showed that chronic DU exposure could induce renal damages and inhibit the synthesis of biologically active form of vitamin D, which may be the underlying mechanism of bone metabolic disorder caused by renal injury after DU exposure.

Uranium isotopes in the Balkan's environment and foods following the use of depleted uranium in the war

Immediately after the Balkan's war in 1999, there has been widespread international concern about the environmental contamination with depleted uranium (DU) from ammunitions used in the conflict. Exposure of military staff and local populations to uranium metal and to its ionizing radiation were feared as potential causes for leukemia and other diseases in that region. In January 2001 a scientific mission was carried out by Portugal to evaluate those issues. A large number of environmental and food samples collected in Kosovo and Bosnia-Herzegovina, such as soils, water, aerosols, vegetables, bread, and meat were analyzed by radiochemistry and alpha spectrometry. Results of the analyses for total uranium and individual uranium isotopes are presented. Uranium in agriculture soils in Kosovo and Bosnia-Herzegovina averaged 1.8+/-0.8mgkg(-)(1) and 3+/-1mgkg(-)(1), while concentrations in drinking water from public supplies averaged 0.5+/-0.2microgL(-)(1) and 0.4+/-0.3microgL(-)(1), respectively. Results on soils indicated also that environmental contamination by DU was much localized and confined to the areas of ammunition impact. Concentrations of uranium in most of the environmental and food samples were comparable to concentrations of uranium measured in other European regions, such as Portugal and United Kingdom, and uranium isotopic ratios were in general compatible with isotopic ratios typical of natural uranium. However, a few samples displayed modified uranium isotopic ratios and could have been contaminated by DU. Implications of DU in radiation exposure of the population and in environmental contamination are discussed.

The toxicity of depleted uranium

Depleted uranium (DU) is an emerging environmental pollutant that is introduced into the environment primarily by military activity. While depleted uranium is less radioactive than natural uranium, it still retains all the chemical toxicity associated with the original element. In large doses the kidney is the target organ for the acute chemical toxicity of this metal, producing potentially lethal tubular necrosis. In contrast, chronic low dose exposure to depleted uranium may not produce a clear and defined set of symptoms. Chronic low-dose, or subacute, exposure to depleted uranium alters the appearance of milestones in developing organisms. Adult animals that were exposed to depleted uranium during development display persistent alterations in behavior, even after cessation of depleted uranium exposure. Adult animals exposed to depleted uranium demonstrate altered behaviors and a variety of alterations to brain chemistry. Despite its reduced level of radioactivity evidence continues to accumulate that depleted uranium, if ingested, may pose a radiologic hazard. The current state of knowledge concerning DU is discussed.

Radiation dose assessment of exposure to depleted uranium

Depleted uranium (DU) is claimed to contribute to human health problems, known as the Gulf War Syndrome and the Balkan Syndrome. Quantitative radiation dose is required to estimate the health risk of DU materials. The influences of the solubility parameters in the human alimentary tract and the respiratory tract systems and the aerosol particles size on the radiation dose of DU materials were evaluated. The dose conversion factor of daily urinary excretion of DU is provided. The retention and excretion of DU in the human body after a contamination at a wound site were predicted. Dose coefficients of DU after ingestion and inhalation were calculated using the solubility parameters of the DU corrosion products in simulated gastric and simulated lung fluid, which were determined in the Helmholtz Zentrum München. (238)U is the main radiation dose contributor per 1 Bq of DU materials. The dose coefficients of DU materials were estimated to be 3.5 x 10(-8) and 2.1 x 10(-6) Sv Bq(-1) after ingestion and inhalation for members of the public. The ingestion dose coefficient of DU materials is about 75% of the natural uranium value. The inhalation dose coefficient of DU material is in between those for Type M and Type S according to the category for inhaled materials defined by the International Commission on Radiological Protection. Radiation dose possibly received from DU materials can directly be estimated by using the dose conversion factor provided in this study, if daily urinary excretion of DU is measured.

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 microg U/g, 16.35 +/- 1.67 microg U/g and 21.64 +/- 3.68 microg U/g in the low-, medium- and high-dose group animals, while values in kidney tissues were 10.66 +/- 1.10 microg U/g, 14.06 +/- 1.28 microg U/g and 17.79 +/- 2.87 microg 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.

Stimulus-evoked glutamate release is diminished by acute exposure to uranium in vitro

Uranium is used in civilian applications, in the manufacture of nuclear fuel, and by the military for munitions and armament, but little information is available on its neurotoxicity. Neurological dysfunctions have been observed after chronic exposure in both animals and humans, but the actions of acute exposure on amino acid neurotransmission have not been investigated. The following study was performed to examine the effects of uranyl ion (UO(2)(+2)) on hippocampal glutamatergic and GABAergic function as possible bases for the neurotoxicity and to assess the direct effects on the exocytotic process. Nominal UO(2)(+2) concentrations were applied to superfused hippocampal synaptosomes to permit estimation of the metal's potency on endogenous transmitter release in the presence and absence of Ca(+2). K(+)-evoked glutamate release was diminished in the range of 10 nM-316 microM UO(2)(+2), resulting in an IC(50) of 1.92 microM. In contrast, the potency of UO(2)(+2) to decrease stimulated GABA release was reduced, producing an IC(50) approximately 2.6 mM. In the absence of Ca(+2) in the superfusion medium there was no systematic change in the magnitude of glutamate or GABA release, suggesting that UO(2)(+2) does not possess Ca(+2)-mimetic properties. The inhibitory potency of UO(2)(+2) on glutamate release is similar to the potencies of other multivalent metal ions, suggesting by inference an action exerted on voltage-sensitive Ca(+2) channels. The bases for the reduced potency to inhibit GABA release is not known, but differential sensitivity to other heavy metals has been reported for glutamate and GABA neurotransmission. These findings indicate a profile of neurotoxicity not unlike that of other metal ions, and indicate the importance of extending subsequent studies to chronic exposure models.