Study of the reproductive effects in rats surgically implanted with depleted uranium for up to 90 days

A Review of Uranium-Induced Reproductive Toxicity

As a heavy metal nuclear fuel, uranium is used in various civil and military projects, resulting in environmental pollution. Uranium can enter the body through the mouth, nose and skin, threatening human health. The reproductive organs are sensitive to uranium. For certain exposure times, doses and modes, uranium can produce toxic effects on the reproductive organs. The reproductive toxicity of uranium can be produced through different mechanisms of action, such as changing the level of sex hormones in the body, disrupting the expression of genes or proteins related to reproduction and causing oxidative stress and inflammation. Uranium thus can cause toxic effects to the reproductive system, leading to histopathological changes and decreased conception rates, and may damage the health of the body. This paper reviews the research progress on uranium reproductive toxicity in recent years and indicates a direction for future research on uranium reproductive toxicity and its mechanisms.

How toxic is the depleted uranium to crayfish Procambarus clarkii compared with cadmium?

Due to a lack of information on the assessment of uranium's (U) toxicity, our work aimed to compare the effects of U on the crayfish Procambarus clarkii with those of the well documented metal: cadmium (Cd). Accumulation and impacts at different levels of biological organization were assessed after acute (40 µM Cd or U; 4-10 days) and chronic (0.1 µM Cd or U; 30-60 days) exposures. The survival rates demonstrated the high tolerance of this species toward both metals and showed that Cd had a greater effect on the sustainability of crayfish. The concentration levels of Cd and U accumulated in gills and hepatopancreas were compared between both conditions. Distinctions in the adsorption capacities and the mobility of the contaminants were suspected. Differences in the detoxification mechanisms of both metals using transmission electron microscopy equiped with an energy dispersive X-ray were also pointed out. In contrast, comparison between the histological structures of contaminated hepatopancreas showed similar symptoms. Principal component analyses revealed different impacts of each metal on the oxidative balance and mitochondria using enzymatic activities and gene expression levels as endpoints. The observation that U seemed to generate more oxidative stress than Cd in our conditions of exposure is discussed.

Uranium quantification in semen by inductively coupled plasma mass spectrometry

In this study we report uranium analysis for human semen samples. Uranium quantification was performed by inductively coupled plasma mass spectrometry. No additives, such as chymotrypsin or bovine serum albumin, were used for semen liquefaction, as they showed significant uranium content. For method validation we spiked 2g aliquots of pooled control semen at three different levels of uranium: low at 5 pg/g, medium at 50 pg/g, and high at 1000 pg/g. The detection limit was determined to be 0.8 pg/g uranium in human semen. The data reproduced within 1.4-7% RSD and spike recoveries were 97-100%. The uranium level of the unspiked, pooled control semen was 2.9 pg/g of semen (n=10). In addition six semen samples from a cohort of Veterans exposed to depleted uranium (DU) in the 1991 Gulf War were analyzed with no knowledge of their exposure history. Uranium levels in the Veterans' semen samples ranged from undetectable (<0.8 pg/g) to 3350 pg/g. This wide concentration range for uranium in semen is consistent with known differences in current DU body burdens in these individuals, some of whom have retained embedded DU fragments.

Toxicity studies on depleted uranium in primary rat cortical neurons and in Caenorhabditis elegans: what have we learned?

Depleted uranium (DU) is the major by-product of the uranium enrichment process for its more radioactive isotopes, retaining approximately 60% of its natural radioactivity. Given its properties as a pyrophoric and dense metal, it has been extensively used in armor and ammunitions. Questions have been raised regarding the possible neurotoxic effects of DU in humans based on follow-up studies in Gulf War veterans, where a decrease in neurocognitive behavior in a small population was noted. Additional studies in rodents indicated that DU readily traverses the blood-brain barrier, accumulates in specific brain regions, and results in increased oxidative stress, altered electrophysiological profiles, and sensorimotor deficits. This review summarizes the toxic potential of DU with emphasis on studies on thiol metabolite levels, high-energy phosphate levels, and isoprostane levels in primary rat cortical neurons. Studies in Caenorhabditis elegans detail the role of metallothioneins, small thiol-rich proteins, in protecting against DU exposure. In addition, recent studies also demonstrate that only one of the two forms, metallothionein-1, is important in the accumulation of uranium in worms.

Uranium in drinking water: effects on mouse oocyte quality

The aim of this work was to evaluate the reproductive toxicological effects of uranium (U) at 2.5, 5, and 10 mgU/kg/d chronically administered in drinking water for 40 d. Swiss female control mice (n = 28) and mice chronically contaminated with uranyl nitrate in drinking water (n = 36) were tested. The number and quality of ovulated oocytes, chromatin organization, and nuclear integrity were evaluated. No significant differences were obtained in the numbers of ovulated oocytes between the different groups. Nevertheless, in 1,520 of the oocytes examined, dysmorphism increased from 11.99% in the control group to 27.99%, 27.19%, and 27.43% in each of the contaminated groups, respectively, in a dose-independent manner. On the other hand, morphological chromatin organization from 880 oocytes examined showed an increase in metaphase plate abnormalities from 37.20% (+/-7.21) in the control group to 55.13% (+/-21.36), 58.29% (+/-21.72), and 64.10% (+/-12.62) in each of the contaminated groups, respectively. Cumulus cell (CC) micronucleation, a parameter of nuclear integrity, increased from 0.21% (+/-0.31) in the control group to 1.92 (+/-0.95), 2.98 (+/-0.97), and 3.2 (+/-0.98), respectively. Both metaphase plate abnormalities and CC micronucleation showed an increase in a dose-dependent manner (r = 0.9; p < 0.001). The oocyte and its microenvironment showed high sensitivity to uranium contamination by drinking water. The lowest observed adverse effect level for this system is estimated at a level below 2.5 mgU/kg/d for female mice.

Two-generation reproductive toxicity study of implanted depleted uranium (DU) in CD rats

Depleted uranium (DU) munitions and armor plating have been used in several conflicts over the last 17 yr, including the Persian Gulf War and the Iraq War. Because of its effectiveness and availability, DU will continue to be used in military applications into the foreseeable future. There is much controversy over the use of DU in weapons and equipment because of its potential radiological and toxic hazards, and there is concern over the chronic adverse health effects of embedded DU shrapnel in war veterans and bystanders. This study evaluated the effects of long-term implantation of DU on the reproductive success of F0 generation adults and development and survival of subsequent F1 and F2 generations in a two-generation reproductive toxicity study. F0 generation Sprague-Dawley rats, 8 wk of age, were surgically implanted with 0, 4, 8, 12, or 20 DU pellets (1 x 2 mm). Inert implant control animals were implanted with 12 or 20 tantallum (Ta) pellets. The F0 generation was then mated at 120 d post DU implantation. In the F0 generation, when measured on postimplantation d 27 and 117, uranium was present in the urine of DU-implanted animals in a dose-dependent manner. F0 reproductive success was similar across treatment groups and the maternal retrieval test revealed no changes in maternal behavior. DU implantation exerted no effect on the survival, health, or well-being of the F0 generation. Necropsy results of F0 animals were negative with the exception of a marked inflammatory response surrounding the implanted DU pellets. For the F1 generation, measures of F1 development through postnatal day (PND) 20 were unremarkable and no gross abnormalities were observed in F1 offspring. No uranium was detected in whole-body homogenates of PND 4 or PND 20 pups. Necropsy findings of F1 PND 20 pups were negative and no instances of ribcage malformation were observed in F1 PND 20 pups. Body weight and body weight gain of F1 rats through PND 120 were similar across treatment groups. Eight of 414 F1 animals observed from PND 20 to 120 died of unknown causes; 7 were from litters of DU-implanted F0 mating pairs. F1 mating success at 10 wk of age was an overall 70% compared with 91% for F0 mating pairs. Mating success was similar between F1 animals derived from DU-implanted F0 adults and those derived from F0 implant control adults suggesting that the comparatively low mating success was not due to F1 DU exposure. The gestational index of F1 animals derived from mid-dose F0 mating pairs was found to be lower compared with F1 controls. The average gestation duration of F1 animals derived from high-dose F0 mating pairs was found to be significantly longer than F1 controls. F1 sperm motility analyses did not differ among experimental groups and no gross abnormalities were identified at necropsy among surviving F1 animals at PND 120. Histopathology of kidneys, spleen, thymus, bone marrow, ovaries, and testes of F1 high-dose animals did not differ from F1 controls. F1 high-dose females had significantly higher mean relative liver and heart weights compared with F1 controls; the biological relevance of this finding could not be determined. For the F2 generation, measures of F2 development through PND 20 were unremarkable and no gross abnormalities were observed in F2 offspring. Necropsy findings of F2 PND 20 pups were negative and no instances of ribcage malformation were observed in F2 PND 20 pups. Body weight and body weight gain of F2 rats through PND 90 were similar across treatment groups. Mean relative heart weights of males derived from high-dose F0 parents were significantly lower compared with F2 controls. Sperm motility and concentration analysis of F2 males at PND 90 were similar across F2 groups. Overall, the consistent absence of positive findings in this study seems to suggest that DU is not a significant reproductive or developmental hazard, particularly when one considers that mid- and high-dose rats were implanted with the equivalent of 0.3 and 0.5 lb of DU in a 70-kg human, respectively. However, the findings that seven of eight F1 adults that died postweaning were from DU-implanted F0 mating pairs, and that mean relative heart weights were elevated in high-dose F1 and F2 pups, suggest conservatism is warranted in characterizing the reproductive and teratogenic hazards of embedded DU until further studies are completed.

Evaluation of the effect of implanted depleted uranium (DU) on adult rat behavior and toxicological endpoints

In 2002, the Naval Health Research Center Toxicology Detachment began a study to determine the effects of surgically implanted depleted uranium (DU) pellets on adult rat (e.g., P1 generation) health and reproduction. In this report, the effect of implanted DU on adult rat behavior and health is described. Adult Sprague-Dawley (SD) rats, 8 wk of age, were surgically implanted with 0, 4, 8, 12, or 20 DU pellets (1 x 2 mm); 20 DU pellets of size 1 x 2 mm approximates to 0.22 kg (0.5 lb) of DU in a 70-kg (154 lb) person. Control animals were implanted with 12 or 20 tantallum (Ta) pellets. The animals were then housed for up to 150 d postimplantation or 20% of an assumed 2-yr life span for rats. The concentration of uranium in urine directly correlated with the number of implanted DU pellets, indicating that DU was migrating into the body from the implanted pellets. Three male and 4 female animals died during the 150-d period of causes apparently not related to DU implantation. Behavioral testing found no definitive evidence of neurobehavioral perturbations associated with DU implantation. Uranium translocated to tissues known to sequester uranium (bone, teeth, and kidneys), but uranium concentrations varied considerably within each dose group and did not follow a dose-response pattern as anticipated. Serum chemistry values were within normal ranges for the SD rat. However, alanine aminotransferase measurements were significantly lower for rats implanted with 20 DU pellets as compared to sham surgery controls but not when compared to animals implanted with Ta pellets only. Phosphate measurements were significantly lower for female rats implanted with 20 DU pellets as compared to both sham surgery controls and animals implanted with Ta pellets only. Monocyte ratios were higher in adult rats implanted with 20 DU pellets as compared to sham surgery controls but not when compared to animals implanted with 20 Ta pellets. Mean platelet volume was found to be significantly lower for rats implanted with 20 DU pellets as compared to sham surgery controls but not when compared to animals implanted with 20 Ta pellets. Gross necropsy found no obvious tissue abnormalities in implanted rats, and the weights of major tissues did not differ between Ta- and DU-implanted animals. Histopathologic analysis of major tissues from animals implanted with 0 pellets, 20 Ta pellets, or 20 DU pellets found no differences between treatment groups. The findings of this study indicate that implantation of up to 20 DU pellets in adult rats did not have a significant negative impact on their general health and neurobehavioral capacities when assessed after 150 d of pellet implantation. However, the growing body of data on the potential health effects associated with DU exposure warrants further studies involving higher embedded DU body burdens in conjunction with longer surveillance periods postimplantation.