Photoperiod affects hepatic and renal cadmium accumulation, metallothionein induction, and cadmium toxicity in the wild bank vole (Clethrionomys glareolus)

Naringenin blocks hepatic cadmium accumulation and suppresses cadmium-induced hepatotoxicity via amelioration of oxidative inflammatory signaling and apoptosis in rats

Liver is one of the targets of cadmium (Cd) bioaccumulation for hepatic damage and pathologies via oxidative inflammation and apoptosis. The current study explored whether the citrus flavonoid naringenin (NAR) could prevent hepatic accumulation of Cd and Cd hepatotoxicity in a rat model. Rats in group 1 received normal saline; group 2 received NAR (50 mg/kg body weight); group 3 received CdCl2 (5 mg/kg body weight); group 4 received NAR + CdCl2, for four consecutive weeks. Assays related to markers of oxidative stress, inflammation, and apoptosis were carried out using liver homogenate. Blood and liver sample analyses revealed significant elevation of blood and hepatic Cd levels coupled with prominent increases in alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activities, whereas the albumin and total protein levels were decreased considerably. Hepatic superoxide dismutase (SOD), catalase (CAT), glutathione peroxide (GPx) activities diminished significantly compared to control followed by marked increases in malondialdehyde (MDA) levels, and dysregulation in caspase and cytokine (TNF-α, IL-6, IL-4, IL-10) levels. However, it was found that in the rats administered NAR + Cd, the levels of Cd, hepatic enzymes, MDA, TNF-α, IL-6, and caspases-3/-9 were prominently reduced compared to the Cd group. The hepatic SOD, CAT, GPx, IL-4, IL-10, albumin, and total protein were markedly elevated along with alleviated hepatic histopathological abrasions. Taken together therefore, NAR is a potential flavonoid for blocking hepatic Cd bioaccumulation and consequent inhibition of Cd-induced oxidative inflammation and apoptotic effects on the liver of rats.

Hepatic effects of low-dose rate radiation in natural mouse populations (Apodemus uralensis and Apodemus agrarius): comparative interspecific analysis

Hypothesis: Natural mouse populations in radioactive contamination zone provide adequate information about dose loads and biological effects for 'non-human biota'. The comparative analysis of the responses of different species of mice allows us to reveal the possible variation in the effects of low-dose rate radiation relative to the ecological-physiological and functional-metabolic features of the species.Materials and methods: Objects of study - two sympatric rodent species [pygmy wood mouse (Apodemus uralensis Pallas, 1811) and striped field mouse (Apodemus agrarius Pallas, 1771)] caught on the territory of the East-Ural radioactive trace (EURT). The EURT zone is consequence the Kyshtym accident in South Urals in 1957. Nowadays, the main dose-forming radionuclide is β-emitting ⁹⁰Sr. The individual dose rate of impacted mice caused by internal exposure to ⁹⁰Sr varied from 0.021 to 0.152 mGy/day. The baseline functional-metabolic characteristics of the liver were researched: protein-, lipid-, and glycogen-synthesizing processes; glycolysis; aerobic synthesis of ATP; lipid peroxidation; and the H₂O₂-scavenging enzymatic status; and the functional activity of the genome.Results: The hepatic shifts for impacted populations are amplified with increasing dose rate of irradiation, regardless of which species is considered. But, the response of closely related species of rodents to irradiation is different both in the vector and the level (in A. agrarius sample was 2 time higher than that for A. uralensis).Conclusion: The radiation-induced hepatic shifts in A. uralensis from the EURT area correspond to the chronic response under stressful environmental conditions. The impacted population of A. agrarius can be considered the more reactive species to the radiation burden, demonstrating an acute effect. The interspecies contrast in the radiation response is associated with the original interspecies differences (background rodents' samples in 28 km from the impact study site), and also the degree of residency of the species in the impact plots.

Chronic exposure to lead and cadmium pollution results in genomic instability in a model biomonitor species (Apodemus flavicollis Melchior, 1834)

Polymetal dust is a common industrial pollutant. While the use of remediation filters and equipment in lead smelters has reduced pollutant emission, surrounding areas remain contaminated due to the long-term transfer of heavy metals along the food chain. Here we assess the mutagenic potential of the lead-zinc smelter near Plovdiv (Bulgaria) situated in an area that has been contaminated with heavy metals for 60 years. We aimed to evaluate the genomic response of the yellow-necked mouse (A. flavicollis), a biomonitor species, in three sampling sites along the pollution gradient. Mice from Strandzha Natural Park were used as a negative control. The bioaccumulation rate of two non-essential heavy metals, lead (Pb) and cadmium (Cd), in liver tissues was determined by atomic absorption spectroscopy. Genetic alterations attributable to chronic exposure to trace levels of heavy metals were assessed in different blood cell populations using two independent methods: a micronucleus test was applied to evaluate the clastogenic and aneugenic alterations in erythrocytes, while a comet assay was used to assess DNA instability, as evidenced by single- and double-stranded breaks and alkali-labile sites, in leucocytes. We observed elevated levels of Pb and Cd in livers derived from mice from the impacted area: the mean Pb concentration (21.38 ± 8.77 μg/g) was two-fold higher than the lowest-observed-adverse-effect levels (LOAELs), while the mean Cd concentration (13.95 ± 9.79 μg/g) was extremely close to these levels. The mean levels of Pb and Cd in livers derived from mice from the impacted area were 31-fold and 63-fold higher, respectively, than the levels measured in mice from the control area. The mean frequency of micronuclei was significantly higher (four-fold) than that observed in the control animals. Furthermore, parameters measured by the comet assay, % tail DNA, tail length and tail moment, were significantly higher in the impact area, indicating the degree of genetic instability caused by exposure to heavy metals. In conclusion, this study shows that despite the reported reduction in lead and cadmium emissions in Bulgaria in recent years, A. flavicollis individuals inhabiting areas subject to long-term contamination exhibit significant signs of DNA damage.

Two novel CYP3A isoforms in marine mussel Mytilus coruscus: Identification and response to cadmium and benzo[a]pyrene

CYP3A enzymes play a crucial role in metabolic clearance of a variety of xenobiotics. However, their genetic information and function remain unclear in molluscs. In the present study, two novel CYP3A genes i.e. McCYP3A-1 and McCYP3A-2 were identified and characterized from the thick shell mussel Mytilus coruscus, and their tissue distribution as well as the response to cadmium (Cd) and benzo[a]pyrene (B[α]P) exposure were addressed using real time quantitative RT-PCR (qRT-PCR) and erythromycin N-demethylase (ERND) assay. McCYP3A-1 and McCYP3A-2 possess typically domains of CYP family such as helix-C, helix-I, helix-K, PERF and the heme binding domain as well as the characteristic domains of CYP3s including six SRS motifs. McCYP3A-1 and McCYP3A-2 transcripts were constitutively expressed in all examined tissues with high expression level in digestive glands, hepatopancreas and gonads. Upon B[α]P exposure, McCYP3A-1 and McCYP3A-2 mRNA expression in digestive glands showed a pattern of up-regulation followed by down-regulation, while under Cd exposure, showed a time-dependent induction profile. In addition, ERND activity, generally used as an indicator of CYP3, increased in a time-dependent manner after exposure to Cd and B[α]P. These results collectively indicated that McCYP3A-1 and McCYP3A-2 are CYP3A family member and may play a potential role in metabolic clearance of xenobiotics. Meanwhile, the current results may provide some baseline data to support McCYP3A-1 and McCYP3A-2 as candidate biomarkers for monitoring of PAHs and heavy metal pollution.

Structural-functional modifications of the liver to chronic radioactive exposure in pygmy wood mouse (Apodemus uralensis) within the East-Urals Radioactive Trace

The hepatic parameters (contents of glycogen, total lipids, nuclear and cytoplasmic proteins, DNA and RNA, fructose-6-phosphate, water, lipid peroxidation products, as well as activities of succinate dehydrogenase and glucose phosphate isomerase), radiometric data, and the relative population abundance of the pygmy wood mouse (Apodemus uralensis Pall., 1811) inhabiting natural (Middle Urals, Southern Urals, and Trans-Urals) areas and radioactivity territory (the EURT zone after of the Kyshtym accident in the South Urals in 1957) were analysed. Structural-functional modifications of the liver in A. uralensis from the EURT area are presented, taking into account irradiation power by dose-forming radionuclides (external and internal exposure to ¹³⁷Cs and ⁹⁰Sr), population size, and reproductive status (sexually immature and sexually mature yearlings, representing different ontogenetic patterns). The sexually immature mice from the EURT area can be considered to be the more sensitive (reactive) intrapopulation group to synergistic factors, such as radiation burden and population overabundance. The extent of structural-functional hepatic modification under current conditions of radionuclide exposure, in addition to the 60 year long effect of radioactive contamination in the EURT, can exceed the level of natural (geographic) variation observed in this species in the Urals region, which points to a long term evolutionary-ecological process.

Histopathology related to cadmium and lead bioaccumulation in chronically exposed wood mice, Apodemus sylvaticus, around a former smelter

The ceasing of industrial activities often reduces the emission of pollutants but also often leaves disturbed areas without remediation and with persistent pollutants that can still be transferred along the food chain. This study examines the potential relationships between non-essential trace metals and histopathology in target tissues of wood mice (Apodemus sylvaticus) collected along a gradient of contamination around the former smelter, Metaleurop Nord (northern France). Cadmium and lead concentrations were measured, and histological alterations attributable to chronic trace metal exposure were assessed in the liver and the kidneys of 78 individuals. Metal concentrations quantified in the present study were among the highest observed for this species. Some histological alterations significantly increased with Cd or Pb concentrations in the soil and in the organs. Sixteen mice from polluted sites were considered at risk for metal-induced stress because their Cd and/or Pb tissue concentrations exceeded the LOAELs for single exposure to these elements. These mice also exhibited a higher severity of histological alterations in their organs than individuals with lower metal burdens. These results indicate that the Metaleurop smelter, despite its closure in 2003, still represents a threat to the local ecosystem because of the high levels and high bioavailability of Cd and Pb in the soil. However, among the mice not considered at risk for metal-induced stress based on the metal levels in their tissues, a large percentage of individuals still exhibited histological alterations. Thus, the present study suggests that the evaluation of toxic effects based only on the LOAELs for single metal exposure may result in the underestimation of the real risks when specimens are exposed to multiple stressors.

Protective effects of Lactobacillus plantarum CCFM8610 against chronic cadmium toxicity in mice indicate routes of protection besides intestinal sequestration

Our previous study confirmed the ability of Lactobacillus plantarum CCFM8610 to protect against acute cadmium (Cd) toxicity in mice. This study was designed to evaluate the protective effects of CCFM8610 against chronic Cd toxicity in mice and to gain insights into the protection mode of this strain. Experimental mice were divided into two groups and exposed to Cd for 8 weeks via drinking water or intraperitoneal injection. Both groups were further divided into four subgroups, control, Cd only, CCFM8610 only, and Cd plus CCFM8610. Levels of Cd were measured in the feces, liver, and kidneys, and alterations of several biomarkers of Cd toxicity were noted. The results showed that when Cd was introduced orally, cotreatment with Cd and CCFM8610 effectively decreased intestinal Cd absorption, reduced Cd accumulation in tissue, alleviated tissue oxidative stress, reversed hepatic and renal damage, and ameliorated the corresponding histopathological changes. When Cd was introduced intraperitoneally, administration of CCFM8610 did not have an impact on tissue Cd accumulation or reverse the activities of antioxidant enzymes. However, CCFM8610 still offered protection against oxidative stress and reversed the alterations of Cd toxicity biomarkers and tissue histopathology. These results suggest that CCFM8610 is effective against chronic cadmium toxicity in mice. Besides intestinal Cd sequestration, CCFM8610 treatment offers direct protection against Cd-induced oxidative stress. We also provide evidence that the latter is unlikely to be mediated via protection against Cd-induced alteration of antioxidant enzyme activities.

Differential susceptibility to cadmium-induced liver and kidney injury in wild and laboratory-bred bank voles Myodes glareolus

The objective of the study was to compare the sensitivity of wild and laboratory-bred bank voles to cadmium (Cd)-induced histopathological changes in the liver and kidneys. For 4 weeks, the male bank voles-both wild and laboratory-bred-were provided with diet containing Cd in quantities <0.1 (control), 30, and 60 μg/g dry weight. At the end of exposure period, histopathology and analyses of Cd, metallothionein (MT), glutathione (GSH), zinc (Zn), copper (Cu), iron (Fe), and lipid peroxidation-all considered to be critical factors during the development of Cd toxicity in the liver and kidneys-were carried out. Histopathological changes (focal hepatocyte swelling, vacuolation and inflammation [leukocyte infiltration] in the liver, and focal proximal tubule degeneration [including epithelial cell swelling] in the kidneys) occurred only in the wild bank voles fed a diet containing 60 μg Cd/g. There were no differences in concentrations of Cd, MT, GSH, Zn, and Cu in liver and kidney between the respective groups of wild and laboratory-bred animals. However, a decrease of hepatic Fe and lipid peroxidation was observed in the wild voles exhibiting histopathological changes. These data indicate the following: (1) wild bank voles are more susceptible to Cd-induced liver and kidney injury than those bred and raised in the laboratory; (2) the difference in sensitivity may be associated with a distinct decrease of hepatic Fe in response to Cd exposure between the two groups of bank voles; and (3) dietary Cd may produce histopathological changes indirectly through decreasing the hepatic Fe and Fe-dependent oxidative processes. These results also suggest that histopathology in the liver and kidney of wild bank voles living in a contaminated environment may occur at relatively low levels of tissue Cd.

Effect of dietary cadmium and/or lead on histopathological changes in the kidneys and liver of bank voles Myodes glareolus kept in different group densities

Bank voles free living in a contaminated environment are known to be more sensitive to cadmium (Cd) toxicity than the rodents exposed to Cd under laboratory conditions, but the reasons for this difference are poorly defined. The present work was designed to determine whether dietary lead (Pb), a common environmental co-contaminant, and/or animal density that affects various physiological processes, would influence susceptibility to Cd toxicity in the kidneys and liver of these animals. For 6 weeks, the female bank voles were kept individually or in a group of six and provided with diet containing environmentally relevant concentrations of Cd [<0.1 μg/g (control) and 60 μg/g dry wt] and Pb [<0.2 μg/g (control) and 300 μg/g dry wt] alone or in combination. At the end of exposure period, histopathology and analyses of metallothionein, glutathione and zinc that are linked to a protective effect against Cd toxicity, as well as Cd, Pb, copper, iron and lipid peroxidation were carried out. Histopathological changes in the kidneys (a focal glomerular swelling and proximal tubule degeneration) and liver (a focal hepatocyte swelling, vacuolation and inflammation) occurred exclusively in some bank voles kept in a group and exposed to Cd alone (2/6) or Cd + Pb (4/6). The observed toxicity in grouped bank voles appeared not to be based on altered (1) tissue disposition of Cd and/or Pb, (2) metallothionein, glutathione and zinc concentrations, or (3) tissue copper, iron and lipid peroxidation. The data indicate that high population density in combination with environmental Pb may be responsible for an increased susceptibility to Cd toxicity observed in bank voles free living in a contaminated environment; the mechanism by which animal density affects Cd toxicity deserves further study.

Combined effect of dietary cadmium and benzo(a)pyrene on metallothionein induction and apoptosis in the liver and kidneys of bank voles

Bank voles free living in a contaminated environment have been shown to be more sensitive to cadmium (Cd) toxicity than the rodents exposed to Cd under laboratory conditions. The objective of this study was to find out whether benzo(a)pyrene (BaP), a common environmental co-contaminant, increases Cd toxicity through inhibition of metallothionein (MT) synthesis-a low molecular weight protein that is considered to be primary intracellular component of the protective mechanism. For 6 weeks, the female bank voles were provided with diet containing Cd [less than 0.1 μg/g (control) and 60 μg/g dry wt.] and BaP (0, 5, and 10 μg/g dry wt.) alone or in combination. At the end of exposure period, apoptosis and analyses of MT, Cd, and zinc (Zn) in the liver and kidneys were carried out. Dietary BaP 5 μg/g did not affect but BaP 10 μg/g potentiated rather than inhibited induction of hepatic and renal MT by Cd, and diminished Cd-induced apoptosis in both organs. The hepatic and renal Zn followed a pattern similar to that of MT, attaining the highest level in the Cd + BaP 10-μg/g group. These data indicate that dietary BaP attenuates rather than exacerbates Cd toxicity in bank voles, probably by potentiating MT synthesis and increasing Zn concentration in the liver and kidneys.

Tissue cadmium accumulation is associated with basal metabolic rate in mice

The objective of this study was to examine relations between basal metabolic rate (BMR) and cadmium (Cd) accumulation in the liver, kidneys, and duodenum in mice. The 5-month-old mice selected for high (H) and low (L) BMR were exposed for 8 weeks to 0, 10, and 100 μg Cd/mL of drinking water. The H-BMR mice showed significantly higher concentrations of Cd in the liver (47-79%), kidneys (61-70%), and duodenum (74-100%) than L-BMR animals. The tissue Cd accumulation also positively correlated with the duodenal iron which, in turn, was positively associated with BMR (Spearman R (s) = 0.81, P = 0.0004). The data indicate that tissue accumulation of Cd in mice is linked to BMR; the correlation between tissue Cd and duodenal iron suggests an involvement of iron transport pathway in the accumulation of Cd.

Orally Administered Melatonin and the Accumulation and Toxicity of Cadmium in the Bank Vole (Myodes Glareolus)

Animal gender and age significantly influence the accumulation and toxicity of heavy metals, including cadmium (Cd). The aim of this study was to determine the effect of orally administered melatonin (6 μg/ml), a known antioxidant and metal chelator, on Cd accumulation and toxicity in one month old females and males (young) and five months old bank voles (old) exposed to dietary Cd (100 μg/g) for six weeks. Compared to the Cd alone group, melatonin co-treatment brought about a decrease of Cd concentration in the liver (17% and 20%) and kidneys (39% and 36%) of young female and male bank voles, respectively, while in old animals increased Cd accumulation in liver (65%) and kidneys (81%) and enhanced consumption of Cd-contaminated food (136%) without any effect on their body mass. The results suggest that orally administered melatonin together with cadmium in young bank voles reduces tissue Cd accumulation possibly through forming stable complexes with this metal but in older rodents, melatonin increases concentration of the metal through increasing consumption of Cd-contaminated food.

Cadmium accumulation, metallothionein and glutathione levels, and histopathological changes in the kidneys and liver of magpie (Pica pica) from a zinc smelter area

The objective of this study was to examine a relationship between cadmium (Cd) accumulation and histopathological changes in the kidneys and liver of magpies (Pica pica) from a zinc smelter area. The concentrations of metallothionein (MT) and glutathione (GSH) that are linked to a protective effect against Cd toxicity were also determined. There was a positive correlation between the concentration of Cd (2.2-17.9 microg/g) and histopathological changes (interstitial inflammation and tubular cell degeneration) in the kidneys (R (s) = 0.87, P = 0.0000). The renal Cd also positively correlated with apoptosis (R (s) = 0.72, P = 0.0005) but the metal did not affect lipid peroxidation. Notably, the average concentration of Cd in the kidneys exceeded MT capacity by about 7 microg/g which is thought to produce renal injury. Importantly, GSH level in the kidneys of magpies from the polluted area dropped to 38% of that observed in the reference birds, probably potentiating Cd toxicity. On the contrary, the liver accumulation of Cd was relatively small (0.88-3.38 microg/g), the hepatic MT capacity exceeded the total concentration of Cd and no association between the hepatic Cd and histopathology was found despite the fact that GSH level was only half that observed in the reference birds. The data suggest that Cd intoxication may be responsible for histopathological changes occurring in the kidneys of free-ranging magpies and that the pathology may be associated with inappropriate amount of renal MT and GSH.

Responses of wild small mammals to a pollution gradient: host factors influence metal and metallothionein levels

We investigated how host factors (species, age, gender) modulated Cd, Pb, Zn, and Cu concentrations, metallothionein levels (MTs) and their relationships in 7 sympatric small mammal species along a pollution gradient. Cd concentrations in liver and kidneys increased with age in all species. Age effect on other metals and MTs differs among species. Gender did not influence metal and MT levels except in the bank vole. Three patterns linking internal metal concentrations and MTs were observed along the gradient: a low metal accumulation with a (i) high (wood mouse) or (ii) low (bank vole) level of MTs accompanied by a slight or no increase of MTs with Cd accumulation; (iii) an elevated metal accumulation with a sharp increase of MTs (common and pygmy shrews). In risk assessment and biomonitoring perspectives, we conclude that measurements of MTs and metals might be associated because they cannot be interpreted properly when considered separately.

Seasonal changes of body iron status determine cadmium accumulation in the wild bank voles

The objective of this study was to examine relations between body iron (Fe) status and cadmium (Cd) accumulation in a small rodent, the bank vole, caught from the wild population in late autumn (November) and early spring (March). The concentrations of Fe in the liver, kidneys, and duodenum in the bank voles from the spring were only 30%, 60%, and 70%, respectively, of those found in the animals from the autumn. An analysis of hematocrit and hemoglobin content of blood showed no significant effect of the season, suggesting that the animals from the spring were not anemic. The exposure to dietary Cd (10 microg/g) for 7 days resulted in 70% higher accumulation of Cd in the liver and kidneys of the spring than autumn bank voles, and the concentration of Cd in the duodenum was 3.5 times higher in the spring animals, despite the fact that relative Cd intake was significantly higher in the autumn bank voles. The data indicate that seasonal changes of body Fe status occurring in the wild bank voles may influence tissue accumulation of Cd.

Bioaccumulation of metals and effects of a landfill in small mammals Part III: Structural alterations

The leachates from the Garraf landfill located in a protected site (NE Spain) contain several potentially toxic substances such as heavy metals. Here we report the histopathological alterations produced by this pollution in wild specimens of an omnivorous species, the wood mouse, Apodemus sylvaticus, and an insectivorous species, the greater white-toothed shrew, Crocidura russula. Hepatic tissue presented the most severe alterations in both the species, namely cell cycle arrest (apoptosis and necrosis), inflammation, preneoplasic nodules, vacuolation and microsteatosis. The kidneys were altered more in the mice (presenting tubular necrosis and dilatation, inflammation, and cylinders) than in the shrews, suggesting that different metabolic pathways render shrews more tolerant to renal toxicity induced by pollutants. No pollution-related alterations were observed in lung, spleen, pancreas, gonads, oesophagus, intestine, or adrenals. We conclude that the two species could be used in conjunction as bioindicators to assess the effects of environmental pollution at different trophic levels.

Ultrastructural alterations in midgut and Malpighian tubules of Boettcherisca peregrina exposure to cadmium and copper

The effects of Cu and Cd at their at their low concentrations (80microg/g diet) on the morphology and ultrastructure of the midgut and Malpighian tubules of Boettcherisca peregrina larvae were observed by light and transmission electron microscopy. After exposure to both metals, the midgut got darker, shorter, and thicker than in control, and many strumae occurred on the surface of the midgut. Similarly, Malpighian tubules got shorter and thinner. Ultrastructural alterations in the midgut included mitochondrial condensation, swelling, and lysis. The rough endoplasmic reticulum (rER) showed dilation and vesiculation. The microvilli were shortened and disorganized. The stored glycogens increased and many mineral spherites appeared along with lipid droplets decreased. Ultrastructural alterations observed in the Malpighian tubules included rER vesiculation and mitochondria swelling with loss of cristae. Shortened and disordered microvilli, increased numbers of large hydropic vacuoles, and mineral spherites were also observed.

Joint effects of dietary cadmium and polychlorinated biphenyls on metallothionein induction, lipid peroxidation and histopathology in the kidneys and liver of bank voles

Free-living bank voles have been shown to be more sensitive to cadmium (Cd) toxicity than the rodents exposed to Cd under laboratory conditions. The present study was designed to find out whether polychlorinated biphenyls (PCBs), common environmental co-contaminants, increase susceptibility to Cd toxicity through inhibition of metallothionein (MT) synthesis-a low molecular weight protein that is considered to be a primary intracellular component of the protective mechanism. For 12 weeks, the male bank voles were provided with diets containing Cd (0.05 microg/g (control) and 10 microg/g dry wt) and PCBs (0, 10 and 50 microg/g dry wt) alone or in combination under long (16 h) and short (8 h) photoperiods. At the end of exposure period, histological examinations and analyses of MT, Cd, Fe and lipid peroxidation in the kidneys and liver were carried out. Dietary PCBs did not affect Cd inducibility of renal MT, but decreased it significantly in the liver; however, no signs of Cd toxicity (measured by histopathology) occurred in both organs. On the contrary, PCBs at the highest dose increased significantly lipid peroxidation in the kidneys and liver (4-fold) only in the bank voles raised under a long photoperiod; the PCB-induced hepatic lipid peroxidation was accompanied by extensive histopathological changes including hepatocyte enlargement, necrosis and steatosis. Co-treatment with dietary Cd significantly suppressed the increase in lipid peroxidation and apparently reduced hepatic damage. These data indicate that (1) dietary PCBs do not enhance Cd toxicity in the kidneys and liver of bank voles and (2) dietary Cd suppresses PCB-induced hepatotoxicity that appears to be photoperiod-dependent.

Cadmium accumulation in deer tongue grass (Panicum clandestinum L.) and potential for trophic transfer to microtine rodents

Site 36 at the Crab Orchard National Wildlife Refuge includes a Cd-contaminated soil dominated by deer tongue grass (Panicum clandestinum L.). Analysis of deer tongue grass from this site indicated that biomass and leaf surface area were reduced and that there was a linear relationship between both plant bioavailable soil Cd and total soil Zn and tissue Cd concentration. The Cd concentrations in stems and leaves were also used to estimate the dietary Cd exposures that might be experienced by prairie voles (Microtus ochrogaster) and pine voles (M. pinetorum) consuming deer tongue grass. Renal and hepatic Cd burdens predicted from exclusive consumption of deer tongue grass would be comparable to those that have resulted in chronic toxicity in rodents. The results suggest that for the contaminated soil at Site 36, conditions could allow for the accumulation of Cd in deer tongue grass to concentrations that may pose an ecological risk.

Cadmium distribution and metallothionein expression in lizard tissues following acute and chronic cadmium intoxication

The present report is an attempt to investigate the influence of intraperitoneal and dietary cadmium exposure on the distribution of cadmium accumulation and induction of metallothionein gene expression in different tissues of the lizard Podarcis sicula. Cadmium accumulation in liver, kidney, ovary, brain and intestine was measured by atomic absorption spectrometry. Metallothionein gene induction was determined by dot blot analyses on the total RNA extracted from the same organs. Our data indicate that cadmium exposure results in significant cadmium uptake, but the patterns of this uptake varies with organ and exposure route. After a single intraperitoneal treatment, concentrations of cadmium and metallothionein transcript are positively correlated in kidney, liver and ovary. Following a dietary cadmium treatment, a positive correlation between the increase of metallothionein mRNA and cadmium accumulation is found in intestine, ovary and kidney, while no correlation is present in liver and brain.

Free-ranging European bisons accumulate more cadmium in the liver and kidneys than domestic cattle in north-eastern Poland

It has been shown that free-ranging big game animals accumulate several-fold more cadmium (Cd) in the liver and kidneys than domestic animals. To examine possible reasons for this difference, in the present work we determined the concentrations of Cd in the liver and kidney cortex of European bisons (n=23) from Białowieza Forest (north-eastern Poland) and domestic cattle (n=15) from the same region; in addition, analyses of Cd in the grasses and soil as well as of soil pH were carried out. The accumulation of Cd in liver and kidney cortex of the female bisons correlated significantly with the age up to 7 years, but stabilized thereafter. The 7-12-year-old bisons had 2.14- and 2.25-fold higher concentrations of Cd in the liver and kidney cortex, respectively, than the age-matched domestic cattle. Notably, the Cd levels in the liver and kidneys of the 8-12-year-old cattle were comparable to those found in the 2-year-old and 4-6-year-old bisons, respectively. The content of Cd in the grasses from Białowieza Forest appeared to be 2.1-fold higher than that in the plants from the pastures. Similarly, the concentration of water-extractable Cd in the soil was 2.7-fold greater in Białowieza Forest than in the pastures, despite the fact that nitric acid-extractable Cd (total Cd) was similar in the soils from the two sites. The concentration of water-extractable Cd in the soil as well as the content of Cd in the grasses inversely correlated with soil pH, which appeared to be significantly lower in Białowieza Forest. These data indicate that soil pH is probably responsible for the higher concentrations of Cd in the feed and tissues of bisons as compared with those of domestic cattle.

The effect of orally administered melatonin on tissue accumulation and toxicity of cadmium in mice

The aim of this study was to determine whether an oral administration of melatonin, a known antioxidant, free radical scavenger and metal chelator, influences tissue accumulation and toxicity of cadmium (Cd) in mice exposed subchronically to the metal. The animals received drinking water containing 50 microg Cd/mL only or with additional 2, 4 or 6 microg/mL melatonin for 8 weeks. Melatonin co-treatment brought about a dose-dependent decrease in the renal, hepatic and intestinal Cd concentrations, and the renal and hepatic metallothionein levels followed a pattern similar to that of the Cd accumulation. Histopathological changes occurred only in the kidneys (glomerular swelling and focal tubular degeneration) in all mice from the Cd alone group. In mice co-treated with melatonin, only slight (2 microg/mL melatonin) or no damage (4 and 6 microg/mL melatonin) was seen. The Cd and melatonin treatments did not affect renal lipid peroxidation and iron concentration. These data indicate that orally administered melatonin together with Cd reduces tissue accumulation of this metal; in particular, the reduction of renal Cd accumulation by melatonin is probably responsible for the prevention of Cd-induced injury in this organ.

Melatonin increases tissue accumulation and toxicity of cadmium in the bank vole (Clethrionomys glareolus)

Recent study has shown that a short photoperiod increases the accumulation and toxicity of cadmium (Cd) in the bank vole as compared to a long photoperiod. Since many of the effects of photoperiod on physiological processes in small mammals are transduced by the pineal gland and its hormone melatonin, in this study the effect of subchronic melatonin injection (7 micromol/kg/day for 6 weeks) on the hepatic, renal and intestinal Cd accumulation in the bank voles raised under a long photoperiod and exposed to dietary Cd (0.9 micromol/g) was examined. Simultaneously, histological examinations of the liver and kidneys, and analyses of metallothionein (MT) and lipid peroxidation were carried out. Melatonin co-treatment brought about a significant increase in the hepatic (61%), renal (79%) and intestinal (77%) Cd concentrations as compared to those in the Cd alone group. However, the concentrations of MT in the liver and kidneys of the Cd + melatonin co-treated bank voles did not differ from those in the Cd alone group. Also, histopathological changes in the liver (infiltration of leukocytes) and kidneys (glomerular swelling and a focal tubular cell degeneration) as well as an increase (2-fold) in the renal lipid peroxidation occurred only in animals from the Cd + melatonin group. These data indicate that (1) subchronic melatonin injection has similar effect on the tissue accumulation and toxicity of Cd to that produced by a short photoperiod and (2) the Cd-induced toxicity in the liver and kidneys of melatonin co-treated bank voles is probably due to increased Cd accumulation and decreased synthesis of MT.

Testicular toxicity induced by dietary cadmium is associated with decreased testicular zinc and increased hepatic and renal metallothionein and zinc in the bank vole (Clethrionomys glareolus)

Mechanism of testicular toxicity induced by dietary cadmium (Cd) has been less investigated than that following acute Cd injection. In the present study we characterized testicular injury in a small rodent, the bank vole, exposed subchronically to dietary Cd in a quantity of 0.9 micromol/g, and determined the importance of some factors (Cd accumulation, metallothionein (MT), oxidative stress, and zinc (Zn)) in the injury. Dietary Cd induced moderate histopathological changes (hemorrhage in interstitium, necrosis and apoptosis in seminiferous tubule epithelium) in young (1 month old) bank voles fed, for 6 weeks, Fe-adequate (1.1-1.4 micromol/g) and Fe-enriched (4.5-4.8 micromol/g) diets. In contrast, adult (5 months old) bank voles appeared to be resistant to the toxic effects of dietary Cd, despite the fact that testicular Cd contents were higher and MT levels lower than those in the young animals. The Cd-induced histopathological changes and apoptosis were accompanied by increased testicular lipid peroxidation, decreased testicular Zn concentration and elevated levels of hepatic and renal MT and Zn. Supplemental dietary Zn (1.7-1.8 micromol/g) prevented the Cd-induced testicular Zn depletion and injury. The data indicate that dietary Cd produces testicular lesions indirectly, through decreasing testicular Zn, which seems to be due to the sequestration of this element by the Cd-induced hepatic and renal MT.

Hepatic and renal cadmium accumulation is associated with mass-specific daily metabolic rate in the bank vole (Clethrionomys glareolus)

Previous study has shown that photoperiod and age affect tissue accumulation of cadmium (Cd) in a small rodent, the bank vole. Since the body mass is also influenced by these factors, the present study was designed to determine whether mass-specific daily metabolic rate might be responsible for differential accumulation of Cd in the liver and kidneys of the short- and long-photoperiod bank voles as well as of the young and old animals. One- and five-month old male bank voles were held under short (8 h light/16 h dark) or long (16 h light/8 h dark) photoperiods and exposed to dietary Cd (100 microg/g) for 6 weeks. The bank voles raised under the short photoperiod and those injected subcutaneously with melatonin (7 micromol/kg/day) under the long photoperiod showed significantly higher concentrations of Cd in the liver (43-60%) and kidneys (40-47%) than the age-matched long-photoperiod animals. The old bank voles accumulated significantly less Cd in both organs than the young animals. These differences in Cd accumulation appeared not to be associated with the relative Cd intake. However, the hepatic and renal Cd levels followed a pattern similar to that of the mass-specific daily metabolic rate (or energy expenditure) and energy assimilation efficiency. These data indicate that mass-specific daily metabolic rate and energy assimilation efficiency (an indicative of digestive and absorptive processes) may be responsible for differential tissue Cd accumulation in the bank vole.