Obesogenic effects of chlorpyrifos and its metabolites during the differentiation of 3T3-L1 preadipocytes.

Chlorpyrifos (CPF) is an organophosphorus pesticide widely and extensively used in agriculture in more than one hundred countries and found ubiquitously in the environment. The present study was aimed at providing a better understanding of the obesogenic potential of CPF and its metabolites, as well as to evaluate their effects on the adipocyte differentiation process. For it, during the initial differentiation process, 3T3-L1 mouse preadipocytes were exposed to different concentrations of CPF, CPF-oxon (CPO), or 3,5,6-trichloropyridinol (TCP), which did not affect cell survival. Results showed how CPF and, to a lesser extent, its metabolite TCP, had a positive metabolic influence over the adipogenic process by fostering an increase in the number of differentiated 3T3-L1 preadipocytes, and by enhancing the capacity to store lipid droplets. These processes seem to occur through the upregulation of the transcription factors CCAAT/enhancer-binding protein α (C/EBPα) and peroxisome proliferator-activated receptor γ (PPARγ), which are related to a significant higher expression of the fatty acid-binding protein 4 (FABP4) adipokine. Based on this finding, CPF exposure could be one of the many factors that contributes to the worldwide increase in the incidence of obesity. However, additional investigations are clearly needed.

Oral exposure to silver nanoparticles increases oxidative stress markers in the liver of male rats and deregulates the insulin signalling pathway and p53 and cleaved caspase 3 protein expression.

The present study was aimed at assessing the impact of AgNPs on the liver of male rats orally exposed to 0, 50, 100 and 200 mg/kg/day of polyvinyl pyrrolidone coated AgNPs (PVP-AgNPs) for 90 days. The induction of apoptotic cell death -by measuring the protein levels of the active form of caspase 3- and the levels of the microtubule-associated protein 1A/1B-light chain (LC3) protein were measured as a marker of the induction of autophagy. PVP-AgNPs caused an increase of the activity of superoxide dismutase (SOD) and catalase (CAT) in the liver of male rats. However, the activity decreased after exposure to high amounts of PVP-AgNPs. Increased protein levels of IRS-1, AKT, GSK3ß and mTOR proteins were observed in a dose-dependent manner. However, these proteins showed a decrease at 200 mg/kg/day. The same pattern was observed for the p53, p21 and cleaved caspase 3 protein levels. The current results suggest that the increase of ROS production by PVP-AgNPs stimulated SOD and CAT activity, as well as IRS-1, AKT, mTOR, p53, p21 and caspase 3 as protective mechanisms of cell survival and preserve DNA fidelity. However, cellular damage by excessive ROS production might induce the depletion of these survival mechanisms at 200 mg/kg/day.

New mechanistic insights on the metabolic-disruptor role of chlorpyrifos in apoE mice: a focus on insulin- and leptin-signalling pathways.

Recently, we have provided evidence, suggesting that mice expressing the human apolipoprotein E3 (apoE3) are more prone to develop an obesity-like phenotype and a diabetic profile when subchronically fed a chlorpyrifos (CPF)-supplemented diet. The aim of the current study was to examine the underlying mechanisms through which CPF alters both insulin- and leptin-signalling pathways in an APOE-dependent manner. Both adult apoE3- and E4-targeted replacement and C57BL/6 mice were exposed to CPF at 0 or 2 mg/kg body weight/day through the diet for 8 consecutive weeks. We determined the expression of JAK2, p-JAK2, STAT3, p-STAT3, SOCS3, IRS-1, p-IRS-1, AKT, p-AKT, GSK3ß, p-GSK3ß, and apoE in the liver, as well as hepatic mRNA levels of pon1, pon2, and pon3. CPF markedly disrupted both leptin and insulin homeostasis, particularly in apoE3 mice. Indeed, only CPF-fed apoE3 mice exhibited an increased phosphorylation ratio of STAT3, as well as increased total SOCS3 protein levels. Similarly, the exposure to CPF drastically reduced the phosphorylation ratio of both AKT and GSK3ß, especially in apoE3 mice. Overall, CPF reduced the expression of the three pon genes, principally in C57BL/6 and apoE3 mice. These results provide notable mechanistic insights on the metabolic effects of the pesticide CPF, and attest the increased vulnerability of apoE3 carriers to its metabolic-disruptor role.

Polyvinyl pyrrolidone-coated silver nanoparticles in a human lung cancer cells: time- and dose-dependent influence over p53 and caspase-3 protein expression and epigenetic effects.

The present study was aimed at providing a better understanding of the influence of silver nanoparticles (AgNPs) on the p53 tumor suppressor protein. Cell line A549 was exposed to a range of concentrations of AgNPs, and a time course (up to 72 h) of cell viability was determined. We also determined the time course of gene and protein expression of p53, p21, murine double minute 2 (MDM2) and caspase-3. The expression of all of these proteins was also determined after daily exposure of the cells to 10 µg/mL of AgNPs for 7 days, or after discontinuous exposure by treating the cells every 3 days, for 15 or 30 days. Moreover, epigenetic changes in the acetylation of the histone H3 protein and in global DNA methylation patterns were determined after 72 h of exposure. Results showed that daily exposure to low doses of AgNPs, or a single exposure to high concentrations for 72 h, decreased gene and protein expression of p53, p21, MDM2 and caspase-3 in A549 cells. In contrast, a discontinuous exposure to low doses or a single exposure to low concentrations for 72 h increased the levels of the active forms of p53 and caspase-3, as well as the p21 and MDM2 protein levels. In addition, exposure to high concentrations of AgNPs for 72 h induced higher levels of global DNA methylation and global histone H3 deacetylation in A549 cells. These results provide new information on the toxic action of AgNPs.

Oral subchronic exposure to silver nanoparticles in rats.

Because of their extremely small size, silver nanoparticles (AgNPs) show unique physical and chemical properties, with specific biological effects, which make them particularly attractive for being used in a number of consumer applications. However, these properties also influence the potential toxicity of AgNPs. In this study, we assessed the potential toxic effects of an in vivo oral sub-chronic exposure to polyvinyl pyrrolidone coated AgNPs (PVP-AgNPs) in adult male rats. We also assessed if oral PVP-AgNPs exposure could alter the levels of various metals (Fe, Mg, Zn and Cu) in tissues. Rats were orally given 0, 50, 100 and 200 mg/kg/day of PVP-AgNPs. Silver (Ag) accumulation in tissues, Ag excretion, biochemical and hematological parameters, metal levels, as well as histopathological changes and subcellular distribution following PVP-AgNPs exposure, were also investigated. After 90 days of treatment, AgNPs were found within hepatic and ileum cells. The major tissue concentration of Ag was found in ileum of treated animals. However, all tissues of PVP-AgNPs-exposed animals showed increased levels of Ag in comparison with those of rats in the control group. No harmful effects in liver and kidney, as well as in biochemical markers were noted at any treatment dose. In addition, no hematological or histopathological changes were found in treated animals. However, significant differences in Cu and Zn levels were found in thymus and brain of PVP-AgNPs-treated rats.

Oxidative stress markers after a race in professional cyclists.

The aim was to determine the levels and activities of the oxidative stress markers in erythrocytes, plasma, and urine after a flat cyclist stage. Eight voluntary male professional trained-cyclists participated in the study. Exercise significantly increased erythrocyte, leukocyte, platelet, and reticulocyte counts. The exercise induced significant increases in the erythrocyte activities of catalase (19.8%) and glutathione reductase (19.2%), while glutathione peroxidase activity decreased significantly (29.3%). Erythrocyte GSSG concentration was significantly increased after exercise (21.4%), whereas GSH was significantly diminished (20.4%). Erythrocyte malondialdehyde levels evidenced a significant decrease 3 h after finishing the stage (44.3%). Plasma malondialdehyde, GSH and GSSG levels significantly decreased after 3 hr recovery (26.8%, 48.6%, and 31.1%, respectively). The exercise significantly increased the F2-isoprostane concentration in urine from 359 ± 71 pg/mg creatinine to 686 ± 139 pg/mg creatinine. In conclusion, a flat cycling stage induced changes in oxidative stress markers in erythrocytes, plasma, and urine of professional cyclists. Urine F2-isoprostane is a more useful biomarker for assessing the effects of acute exercise than the traditional malondialdehyde measurement.

Perinatal exposure to BDE-99 causes decreased protein levels of cyclin D1 via GSK3ß activation and increased ROS production in rat pup livers.

We here examined the potential liver toxicity in rat pups from dams exposed during the gestational and lactation periods to 2,2',4,4',5-pentabromodiphenyl ether (BDE-99). Dams were exposed to 0, 1, and 2mg/kg/day of BDE-99 from gestation day 6 to postnatal day 21. When the pups were weaning, the liver from 1 pup of each litter was excised to evaluate oxidative stress markers and the messenger RNA (mRNA) expression of multiple cytochrome P450 (CYP) isoforms. To determine whether thyroid hormone (TH) was disrupted, the protein and mRNA expressions of several TH receptor (TR) isoforms, as well as the protein levels of cyclin D1 and the phosphorylated protein kinases Akt and glycogen synthase kinase 3 beta (GSK3ß), were evaluated. Perinatal exposure to BDE-99 produced decreased levels of cyclin D1 in rat pup livers. A decrease in the active form of Akt and an increase in the active form of GSK3ß were observed. The decreased Akt pathway may be due to a potential disruption of the nongenomic actions of TH by BDE-99 and its metabolites. This possible TH disruption was noted as a decrease in TR isoforms expression. By contrast, we observed an upregulation of CYP2B1 gene expression, which is correlated with an increase in reactive oxygen species production. This outcome indicates activation of the nuclear constitutive androstane receptor, which could induce the expression of other enzymes capable of metabolizing TH. The present findings support the hypothesis that perinatal exposure to PBDEs, at levels found in humans, may have serious implications for metabolic processes in rat pup livers.

Perinatal exposure to BDE-99 causes learning disorders and decreases serum thyroid hormone levels and BDNF gene expression in hippocampus in rat offspring.

Exposure of pregnant women to polybrominated diphenyl ethers (PBDEs) may mean serious health risks. The main goal of the present study was to examine the neurobehavioral changes in rat offspring that were perinatally exposed to one of the most prevalent PBDEs congeners found in humans, 2,2',4,4',5-pentaBDE (BDE-99). Rat dams were exposed to 0, 1 and 2mg/kg/day of BDE-99 from gestation day 6 to post-natal day 21. When pups were weaning, cortex and hippocampal gene expressions of brain-derived neurotrophic factor (BDNF) of the different isoforms of the thyroid hormone (TH) receptors (TRs) were evaluated. Serum TH levels were also determined. The remaining pups were assessed by neurobehavioral testing for learning and memory function. The results showed that maternal transference of BDE-99 produced a delay in the spatial learning task in the water maze test. Moreover, the open-field test revealed a significant dose-response anxiolytic effect. It was also found that the serum levels of triiodothyronine (T3), tetraiiodothyronine (T4) and free-T4 (FT4) decreased. Although no effect on the gene expression of the different isoforms of TRs was observed, the expression of the TH-mediated gene BDNF was down-regulated in the hippocampus. These results indicate a clear signal disruption of TH and reinforce previous studies in which neurotoxic effects of PBDEs in animal research were observed at levels comparable to those found in humans.

Gestational exposure to BDE-99 produces toxicity through upregulation of CYP isoforms and ROS production in the fetal rat liver.

On gestation day (GD) 6 to GD 19, pregnant Sprague Dawley rats were orally exposed to 0, 0.5, 1, and 2 mg/kg/day to one of the most prevalent polybrominated diphenyl ethers congeners found in humans, 2,2',4,4',5-pentaBDE (BDE-99). All dams were euthanized on GD 20, and live fetuses were evaluated for sex, body weight, and external, internal, and skeletal malformations and developmental variations. The liver from one fetus of each litter was excised for the evaluation of oxidative stress markers and the messenger RNA expression of multiple cytochrome P450 (CYP) isoforms. Exposure to BDE-99 during the gestational period produced delayed ossification, slight hypertrophy of the heart, and enlargement of the liver in fetuses. A transplacental effect of BDE-99, evidenced by the activation of nuclear hormones receptors that induce the upregulation of CYP1A1, CYP1A2, CYP2B1, and CYP3A2 isoforms, was also found in fetal liver. These isoforms are correlated with the activity level of the enzyme catalase and the levels of thiobarbituric acid reactive substances. However, teratogenic effects from BDE-99 exposure were not observed. Clear signs of embryo/fetal toxicity, due to a possible hormonal disruption, were evidenced by a large increase in the CYP system and the production of reactive oxygen species in fetal liver.

BDE-99 deregulates BDNF, Bcl-2 and the mRNA expression of thyroid receptor isoforms in rat cerebellar granular neurons.

Although the disruption of thyroid hormone (TH) signaling can largely explain the neurotoxic effects of polybrominated diphenyl ethers (PBDEs), there are still many unknowns about how this interference occurs. In this study, we expose a primary culture of rat cerebellar granule neurons (CGNs) to a 25µM concentration of one of the most prevalent PBDE congeners in humans, 2,2',4,4',5-pentaBDE (BDE-99). The main goal was to investigate the time course of BDE-99 toxicity in relation to the disruption of thyroid receptor (TR) function over 24h. In a first stage, we found that BDE-99 directly down-regulated the transcription of the isoforms TR-alpha1 and TR-alpha2, which may be a consequence of a hypothetical state that mimics hyperthyroidism. In a later stage, BDE-99 disrupted the expression of triiodothyronine (T3)-responsive genes, possibly as an effect of its metabolism. A down-regulation of the expression of the T3-mediated neurotrophin brain-derived neurotrophic factor (BDNF) and the anti-apoptotic Bcl-2 protein was also observed. Down-regulation of these two proteins was correlated with an increase in the production of reactive oxygen species (ROS). It was also found that expression of the TR-beta1 isoform, which is normally transcriptionally repressed by T3 in CGNs, was up-regulated. This up-regulation could compensate the down-regulation of the TR-alpha1 isoform, and thus slow down cell death. The dually disruptive action of BDE-99 might provide a better understanding of the potentially neurotoxic mechanism of PBDEs.

Effects of BDE-99 on hormone homeostasis and biochemical parameters in adult male rats.

In this study, we evaluated the effects of BDE-99 on hormone homeostasis, as well as in urinary and serum biochemical parameters of adult male rats. Animals (10 per group) received BDE-99 by gavage at single doses of 0, 0.6 and 1.2mg/kg. Forty-five days after BDE-99 exposure, urine and serum samples were collected for hormonal and biochemical analysis. Oxidative stress (OS) markers in erythrocytes, plasma and urine were also evaluated. Urinary excretion of total protein significantly increased following BDE-99 exposure, while lactate dehydrogenase (LDH), gamma-glutamil transferase (GGT), and N-acetylglucosaminidase (NAG) activities significantly decreased. Liver toxicity was evidenced by elevated serum activities of the enzymes glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT) and alkaline phosphatase (ALP). Following BDE-99 administration, OS markers in erythrocytes showed an increase in superoxide dismutase (SOD) activity, and a reduction in glutathione reductase (GR) activity. In urine, isoprostane levels increased after BDE-99 exposure. The hormonal analysis showed a significant decrease in testosterone and progesterone levels. These results support the hypothesis that BDE-99 interacts with hormonal response. Moreover, BDE-99 administration to adult male rats showed signs of renal and hepatic toxicity.

Effects of exposure to BDE-99 on oxidative status of liver and kidney in adult rats.

Little is known about the potential toxicity of polybrominated diphenyl ethers (PBDEs) on hepatic and renal tissues. In this study, we investigated the modifications in endogenous antioxidant capacity and oxidative damage in liver and kidney of rats by exposure to one of the most persistent PBDE congeners, the 2,2',4,4',5-pentabromodiphenyl ether (BDE-99). Adult male rats (10 per group) received BDE-99 by gavage at a single dose of 0, 0.6, and 1.2mg/kg body weight. Forty-five days after exposure, liver and kidney were removed and processed to examine the following oxidative stress (OS) markers: reduced glutathione (GSH), oxidized glutathione (GSSG), glutathione reductase (GR), glutathione peroxidase (GPx), glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), and thiobarbituric acid reactive substances (TBARS). In liver, BDE-99 significantly increased SOD activity, GSSG levels, and GSSG/GSH ratio, while GSH levels decreased. Moreover, CAT activity was only reduced at the highest BDE-99 dose. In kidney, CAT activity was significantly decreased, while GSSG/GSH ratio significantly increased following BDE-99 exposure at 1.2mg/kg body weight. Histological examination of tissues showed phagolysosomes in the kidneys of BDE-99-exposed rats. The results of this investigation suggest that acute oral BDE-99 exposure causes renal and liver impairment, being oxidative damage a potential mechanism for nephrotoxicity and hepatotoxicity.

Behavioral effects and oxidative status in brain regions of adult rats exposed to BDE-99.

Polybrominated diphenyl ethers (PBDEs) are used as flame retardants. Although developmental neurotoxicity of PBDEs has been already investigated, little is still known about their potential neurotoxic effects in adulthood. In this study, we assessed the oxidative damage in brain sections and the possible behavioral effects induced by exposure to 2,2',4,4',5-pentabromodiphenyl ether (BDE-99). Adult male rats (10/group) received BDE-99 by gavage at single doses of 0, 0.6 or 1.2mg/kg/body weight. Forty-five days after exposure, the following behavioral tests were conducted: open-field activity, passive avoidance and Morris water maze. Moreover, cortex, hippocampus and cerebellum were processed to examine the following oxidative stress (OS) markers: reduced glutathione (GSH), oxidized glutathione (GSSG), glutathione reductase (GR), glutathione peroxidase (GPx), glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT) and thiobarbituric acid reactive substances (TBARS). In cerebellum, BDE-99 significantly decreased SOD, CAT and GR activities at the highest BDE-99 dose. A decrease in CAT and SOD activities was also observed in cortex and hippocampus, respectively. In the behavioral tests, no BDE-99 effects were observed, while histopathological examination of the brain regions was normal. The current results show that the brain antioxidant capacity is affected by BDE-99 exposure, mainly in cerebellum. Oxidative damage could be a mechanism for BDE-99 neurotoxicity in adult rats.

Sulfasalazine induced oxidative stress: a possible mechanism of male infertility.

The mechanism of action of sulfasalazine (SASP) in male infertility is not well elucidated. For it, an oxidative stress-like mechanism inductor of infertility was hypothesized. Adult male Sprague-Dawley rats (20/group) were orally administered 0, 300, and 600mg SASP/kg body weight for 14 days. One-half of animals in each group remained an additional period of 14 days without treatment. SASP induced a significant decrease of superoxide dismutase (SOD) and glutathione reductase (GR) at the highest dose in both testis and epididymis. GR remained altered in these tissues within the recovery period. However, an increase in SOD was noted in epididymis. An increase in thiobarbituric acid-reactive substances (TBARS) was noted in all SASP-treated groups. In epididymis, catalase (CAT) significantly increased at 600mg/(kgday). These results suggest that SASP induces oxidative stress, which in turn might act as a possible mechanism of male-induced infertility.

Lipid peroxidation and antioxidant status in kidney and liver of rats treated with sulfasalazine.

Sulfasalazine (SASP) is a drug commonly used in the treatment of inflammatory bowel diseases (IBD). In this study, the changes in endogenous antioxidant capacity and oxidative damage in liver and kidney of SASP-treated rats were investigated. Adult male Sprague-Dawley rats were orally given 0, 300, or 600 mg SASP/kg body weight for 14 days. One half of the animals in each group remained 14 additional days without SASP treatment. At the end of the experimental period, rats were euthanized and liver and kidney were removed. In both organs, the following stress markers were determined: reduced glutathione (GSH), oxidized glutathione (GSSG), glutathione reductase (GR), glutathione peroxidase (GPx), glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), and thiobarbituric acid-reactive substances (TBARS). Moreover, histological examination of kidneys showed phagolysosomes after 14 days of SASP withdrawal. A dropsical degeneration was also observed in renal tissue. Oral SASP administration induced a significant increase in TBARS levels in both liver and kidney. After 2 weeks without SASP administration, a recovery of these levels was noted. SOD activity was significantly reduced, while CAT activity significantly increased at 600 mg SASP/(kg day). In kidney, GPx activity significantly increased, while GST activity and GSH levels were significantly reduced at 600 mg SASP/(kg day). These results suggest that in male rats, oxidative damage can be a mechanism for nephro- and hepatotoxicity related with SASP treatment.

Melatonin reduces uranium-induced nephrotoxicity in rats.

The protective role of exogenous melatonin on U-induced nephrotoxicity was investigated in rats. Animals were given single doses of uranyl acetate dihydrate (UAD) at 5 mg/kg (subcutaneous), melatonin at 10 or 20 mg/kg (intraperitoneal), and UAD (5 mg/kg) plus melatonin (10 or 20 mg/kg), or vehicle (control group). In comparison with the UAD-treated group only, significant beneficial changes were noted in some urinary and serum parameters of rats concurrently exposed to UAD and melatonin. The increase of U excretion after UAD administration was accompanied by a significant reduction in the renal content of U when melatonin was given at a dose of 20 mg/kg. Melatonin also reduced the severity of the U-induced histological alterations in kidney. In renal tissue, the activity of the superoxide dismutase (SOD) and the thiobarbituric acid reactive substances (TBARS) levels increased significantly as a result of UAD exposure. Following UAD administration, oxidative stress markers in erythrocytes showed a reduction in SOD activity and an increase in TBARS levels, which were significantly restored by melatonin administration. In plasma, reduced glutathione (GSH) and its oxidized form (GSSG) were also altered in UAD-exposed rats. However, only the GSSG/GSH ratio was restored to control levels after melatonin treatment. Oxidative damage was observed in kidneys. Melatonin administration partially restored these adverse effects. It is concluded that melatonin offers some benefit as a potential agent to treat acute U-induced nephrotoxicity.

Pro-oxidant effects in the brain of rats concurrently exposed to uranium and stress.

Metal toxicity may be associated with increased rates of reactive oxygen species (ROS) generation within the central nervous system (CNS). Although the kidney is the main target organ for uranium (U) toxicity, this metal can also accumulate in brain. In this study, we investigated the modifications on endogenous antioxidant capacity and oxidative damage in several areas of the brain of U-exposed rats. Eight groups of adult male rats received uranyl acetate dihydrate (UAD) in the drinking water at 0, 10, 20, and 40 mg/kg/day for 3 months. Animals in four groups were concurrently subjected to restraint stress during 2h/day throughout the study. At the end of the experimental period, cortex, hippocampus and cerebellum were removed and processed to examine the following stress markers: reduced glutathione (GSH), oxidized glutathione (GSSG), glutathione reductase (GR), glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), thiobarbituric acid reactive substances (TBARS), as well as U concentrations. The results show that U significantly accumulated in hippocampus, cerebellum and cortex after 3 months of exposure. Moreover, UAD exposure promoted oxidative stress in these cerebral tissues. In cortex and cerebellum, TBARS levels were positively correlated with the U content, while in cerebellum GSSG and GSH levels were positively and negatively correlated, respectively, with U concentrations. In hippocampus, CAT and SOD activities were positively correlated with U concentration. The present results suggest that chronic oral exposure to UAD can cause progressive perturbations on physiological brain levels of oxidative stress markers. Although at the current UAD doses restraint scarcely showed additional adverse effects, its potential influence should not be underrated.

Exposure of pregnant rats to uranium and restraint stress: effects on postnatal development and behavior of the offspring.

The effects on postnatal development and behavior were assessed in the offspring of female rats concurrently exposed to uranium (U) and restraint stress. Adult female rats were administered uranyl acetate dihydrate (UAD) in the drinking water at doses of 0, 40 and 80 mg/(kg day) for 4 weeks before mating with untreated males, as well as during pregnancy and lactation. One-half of female rats in each group were concurrently subjected to restraint (2h/day). On gestation day 14, one-half of restrained and unrestrained rats were sacrificed in order to evaluate maternal toxicity and gestational parameters. Pups were evaluated for physical development, neuromotor maturation, and behavior. Uranium concentrations were also determined in various tissues of dams and fetuses. In all uranium-treated groups, the highest concentrations of this element were found in kidney and bone, being considerably higher than those in brain. Uranium levels in tissues of dam or fetuses were not significantly affected by restraint. No significant interactions between uranium and restraint could be observed in maternal toxicity. Moreover, no relevant effects of uranium, maternal restraint, or their combination were noted on developmental landmarks in the offspring. In the passive avoidance test, at 40 and 80 mg UAD/(kg day) restraint significantly modified passive avoidance acquisition (T1) and retention time (T2) 24h later. However, no significant differences were observed on the Morris water maze test. The results of the present study indicate that, in general terms, exposure of female rats to UAD before mating with untreated males, as well as during gestation and lactation, did not cause relevant dose-related adverse effects on postnatal development and behavior of the offspring. The influence of stress was very limited.

Assessment of the pro-oxidant activity of uranium in kidney and testis of rats.

The pro-oxidant activity of uranium (U) was assessed in kidney and testes of male rats, tissues in which toxic effects of this metal are well established. Eight groups of Sprague-Dawley rats received uranyl acetate dihydrate (UAD) in the drinking water at 0, 10, 20, and 40 mg/kgday for 3 months. Rats in four groups were concurrently subjected to restraint during 2 h/day throughout the study. Histopathological examination of the kidneys revealed an angiomatose transformation in U-treated animals. In kidney, thiobarbituric acid-reactive substances (TBARS) levels and oxidized glutathione (GSSG) activity were correlated with U exposure. The superoxide dismutase (SOD) activity was significantly enhanced in both kidney and testis. Oral UAD administration induced a decrease of glutathione reductase (GR) and reduced glutathione (GSH) in the male reproductive tract. The results of this study suggest that graded doses of U elicit depletion of the antioxidant defence system of the rat and induce oxidative stress in testes and kidneys. Although at the current U doses, restraint stress scarcely showed additional adverse effects, its potential influence should not be underrated.

Combined action of uranium and stress in the rat. I. Behavioral effects.

The influence of restraint stress on uranium (U)-induced behavioral effects was assessed in adult male rats. Eight groups of animals received uranyl acetate dihydrate (UAD) in the drinking water at doses of 0, 10, 20 and 40 mg/kg/day during 3 months. Rats in four groups were concurrently subjected to restraint during 2 h per day throughout the study. At the end of the period of uranium exposure, the following behavioral tests were carried out: open-field activity, passive avoidance and Morris water maze. Uranium concentrations in brain were also determined. At 10 and 20 mg/kg/day of UAD restraint significantly affected the total distance traveled in the open-field during the first and third periods tested, respectively, while no significant differences between groups were observed on the passive avoidance test. In the Morris water maze test, the influence of restraint was only significant on the latency time measured on Day 3 in rats exposed at 10 mg/kg/day. Restraint stress did not affect significantly the uranium levels in brain of rats. Although the results of the present study scarcely show uranium-induced behavioral effects at the oral doses of UAD here administered, these effects, as well as the slight influence of restraint stress noted in some tests should not be underrated.