Effects of interaction between65Zn,cadmium, and copper in rats

Distribution and retention of zinc in the presence of cadmium and copper was studied in rats exposed repeatedly to these metals. The experiment was performed on white rats of the Wistar strain. The animals were divided into four groups/five rats each: 1)⁶⁵ZnCl₂; 2)⁶⁵ZnCl₂+CdCl₂; 3)⁶⁵ZnCl₂+CuCl₂; and 4) control group. Rats were administered sc every other day for two weeks:⁶⁵ZnCl₂−5 mg Zn/kg; CdCl₂−0,3 Cd/kg; and CuCl₂−2 mg Cu/kg. The zinc content was measured in rat tissues by γ-counting. Effect of Cd and Cu on subcellular distribution of zinc in the kidney and liver and on the level of metallothionein were also examined. Whole body retention of zinc under the influence of cadmium was lower than that observed in animals treated with zinc alone. However, copper increased twofold the whole body retention of zinc. Cadmium elevated the accumulation of zinc only in the kidneys nuclear fraction and liver soluble fraction. In the kidneys and liver, copper elevated the accumulation of zinc, in the nuclear, mitochondrial, and soluble fractions. The level of metallothionein-like proteins (MT) in the kidneys after a combined supply of zinc and copper was significantly increased with respect to the group of animals treated with zinc alone. These results indicated complex interactions between cadmium, copper, and zinc that can affect the metabolism of each of the metals.     

Effects of zinc pre-treatment on blood glutathione,serum zinc and kidney histological organisation in male rats exposed to cadmium

The effects of sub-chronic exposure to cadmium (Cd) on the blood glutathione, serum zinc and on the kidney histological organisation in rats as well as the possible protective role of zinc (Zn) are the object of this study. For this purpose, 60 male Wistar rats (8 weeks old) were divided into three groups: the first group was exposed to Cd in the form of CdCl₂, administered in five doses (each of 0.4 mg Cd/kg b.w.) on days 5, 10, 15, 20 and 25, giving a total dose of 2 mg Cd/kg b.w., i.p.; the second group was simultaneously exposed to Zn and Cd with the same timeline and the same doses of Cd as the first group but with, in addition, injections of Zn in the form of ZnCl₂, administered in doses of 0.8 mg Zn/kg b.w., giving a total dose of 4 mg Zn/kg b w, i.p.; a control group received 0.5 mL of physiological saline in an identical manner. Intoxication with Cd was followed by a significant decrease in blood glutathione, increase in oxidized glutathione as well as histological damage in kidneys. Pre-treatment with Zn exhibited a protective role against Cd toxicity with a significant decrease in serum zinc content. This fact may be explained by an excessive use of zinc in metallothionein synthesis as a cadmium detoxification agent.     

Acute toxicity of cadmium and zinc in the earthworm (Lumbricus terrestris)

Studies are continuing to explore the use of the earthworm (Lumbricus terrestris) for the determination of the acute toxicity of metal compounds. Worms were injected intraperitoneally with cadmium and zinc chlorides, and also zinc chloride followed by cadmium chloride to see if zinc could protect against the toxicity of cadmium. The 48 h acute toxicity (LD₅₀) values were 22 and 23 mg/kg for Cd and Zn respectively and 30 mg/kg for Cd after the worms were pretreated with Zn. It appears that the earthworm can be a useful test subject for obtaining preliminary information on metal toxicity.     

Hepatoprotective Potentials of Onion and Garlic Extracts on Cadmium-Induced Oxidative Damage in Rats

The hepatoprotective effect of onion and garlic extracts on cadmium (Cd)-induced oxidative damage in rats is reported. Control group received double-distilled water alone. Cd group was challenged with 3CdSO₄·8H₂O (as Cd; 1.5 mg/kg bw per day per oral) alone, while extract-treated groups were pretreated with varied doses of onion and/or garlic extract (0.5 and 1.0 ml/100 g bw per day per oral) for a week and thereafter co-treated with Cd (1.5 mg/kg bw per day per oral) for 3 weeks. Cd caused a marked (p?<?0.001) increase in the levels of lipid peroxidation and glutathione S-transferase, whereas glutathione, superoxide dismutase, and catalase levels were decreased in the liver. We also observed a decrease in hepatic activities of alanine transaminase (ALT), aspartate transaminase (AST), and alkaline phosphatase and a concomitant increase in the plasma activities of ALT and AST. Onion and garlic extracts significantly attenuated these adverse effects of Cd. Onion extract proffered a dose-dependent hepatoprotection. Our study showed that Cd-induced oxidative damage in rat liver is amenable to attenuation by high dose of onion and moderate dose of garlic extracts possibly via reduced lipid peroxidation and enhanced antioxidant defense system that is insufficient to prevent and protect Cd-induced hepatotoxicity.     

Hepatoprotective Effect of Arctium lappa Root Extract on Cadmium Toxicity in Adult Wistar Rats

This study was performed to determine the effects of Arctium lappa (Al) to protect against cadmium damage in the rat liver. Male rats received a single i.p. dose of CdCl₂ (1.2 mg/kg body weight (BW)) with or without Al extract administered daily by gavage (300 mg/kg BW) for 7 or 56 days. After 7 days, Al caused plasma transaminase activity to diminish in groups Al (glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT)) and CdAl (GPT). After 56 days, GOT and GPT plasma activities were reduced in the Cd group. No alteration in plasma levels of creatinine, total bilirubin, and total protein were observed. GOT liver activity increased in the Cd group. No alteration was observed in superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), and malondialdehyde (MDA) dosage. In the Cd group, hepatocyte proportion decreased and sinusoid capillary proportion increased. In the Al and CdAl groups, the nuclear proportion increased and the cytoplasmic proportion decreased. The hepatocyte nucleus density reduced in Cd and increased in the Al group. After 56 days, there was no alteration in the Cd group. In Al and CdAl groups, the nuclear proportion increased without cytoplasmic proportion variation, but the sinusoid capillary proportion was reduced. The hepatocyte nucleus density decreased in the Cd group and increased in the Al and CdAl groups. In conclusion, the liver function indicators showed that A. lappa protected the liver against cadmium toxicity damage.     

Zinc to cadmium replacement in the A. thaliana SUPERMAN Cys₂ His₂ zinc finger induces structural rearrangements of typical DNA base determinant positions

Among heavy metals, whose toxicity cause a steadily increasing of environmental pollution, cadmium is of special concern due to its relatively high mobility in soils and potential toxicity at low concentrations. Given their ubiquitous role, zinc fingers domains have been proposed as mediators for the toxic and carcinogenic effects exerted by xenobiotic metals. To verify the structural effects of zinc replacement by cadmium in zinc fingers, we have determined the high resolution structure of the single Cys₂His₂ zinc finger of the Arabidopsis thaliana SUPERMAN protein (SUP37) complexed to the cadmium ion by means of UV–vis and NMR techniques. SUP37 is able to bind Cd(II), though with a dissociation constant higher than that measured for Zn(II). Cd‐SUP37 retains the ββα fold but experiences a global structural rearrangement affecting both the relative orientation of the secondary structure elements and the position of side chains involved in DNA recognition: among them Ser17 side chain, which we show to be essential for DNA binding, experiences the largest displacement. © 2011 Wiley Periodicals, Inc. Biopolymers 95: 801‐810, 2011.     

Dose–response assessment of metal toxicity upon indigenous Thiobacillus thiooxidans BC1

This study provides a first attempt from a toxicological perspective to put forward, in general terms and explanations, the toxicity series of Cd(II), Cu(II) and Zn(II) to Thiobacillus thiooxidans BC1. Sulphur oxidation and sulphuric acid production are strongly related to microbial growth at pH less than 4. Dose–response analysis on chronic and acute toxicity (e.g. EC₂₀, median effective dose EC₅₀ and slope factor B) of divalent cadmium, copper and zinc cations suggests a toxicity series of Cu>Cd>>Zn to T. thiooxidans BC1. Zn(II) is termed non-toxic and the maximum treatment concentrations of Cd(II) and Cu(II) are approximately 300, 400 mg/l, respectively. This assessment clearly indicates viable operation ranges of metal bioleaching for mine wastewater treatment, suggesting a technological feasibility of biotreatment using acidophilic thiobacilli T. thiooxidans BC1.     

The effects of sublethal concentrations of zinc,cadmium and mercury on Euglena

Results on the effect of sub-lethal concentrations of zinc chloride (ZnCl₂), cadmium chloride (CdCl₂), and mercuric chloride (HgCl₂) on Euglena are presented. During the growth cycle respiratory oxygen uptake and photosynthetic oxygen evolution in the light are initially strongly inhibited by Zn, Cd and Hg. The effects of the three metals on photosynthesis, using oxygen evolution as a criterion was confirmed by carbon fixation techniques.Photosystem I (PSI) associated electron transport 2,6-dichlorophenol indophenol (DCPIP)_red. methyl viologen (MV) O₂, in contrast to total photosynthetic capacity, was only slightly inhibited by Zn, Cd and Hg, whereas the levels of activity of NADP-oxidoreductase in cells untreated or treated with heavy metals showed development like total photosynthesis. Metals strongly inhibited this enzyme which means that the supply of NADPH is lowered due to the action of Zn, Cd and Hg. Photosystem II (PSII) associated electron transport (H₂O dibromothymoquinone/2,3-dimethyl-5,6-methylenedioxy-D-benzoquinone O₂), however, was severely inhibited in a way similar to total photosynthesis. Effects on the cooperation of PSI + II showed patterns similar to PSII alone, i.e., heavy metals strongly reduced PSI + II dependent activities.Abbreviations DAD diaminodurene - DBMIB dibromothymoquinone - DCPIP 2,6-dichlorophenolindophenol - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DMMIB 2,3-dimethyl-5,6-methylenedioxy-p-benzoquinone - DPC 1,5-diphenylcarbazide - MV methylviologen - PS photosystem Dedicated to Professor Kandler on occasion of his 60th birthday     

Zinc-selenium interaction in the rat

Retention, dynamics of⁷⁵Se and⁶⁵Zn distribution, and elimination were studied in rats after separate or joint single doses of these metals. White female Wistar rats were divided into four groups (fifteen rats each). Group I received Na₂ ⁷⁵SeO₃ (0.1 mg Se/kg i.g.), group II received Na₂ ⁷⁵SeO₃+ZnCl₂ (5 mg Zn/kg s.c.), group III received⁶⁵ZnCl₂, and group IV received⁶⁵ZnCl₂+Na₂SeO₃. The zinc and selenium contents in the tissues were estimated during 120 h after administration; excretion in urine and feces of animals was determined throughout the experiment. Combined administration of zinc and selenium resulted in an enhanced selenium retention in the brain, spleen, kidneys, blood, lungs, and heart. A selenium-induced increase in the concentration of zinc was noted in the bowels, blood, liver, kidneys, spleen, brain, and lungs. The effects of the zinc/selenium interaction were visible especially in the lowered level of excretion of these elements. Zinc induced a decrease in the excretion of selenium in urine, with no concomitant changes in the excretion in feces. However, a visible decrease in the excretion of zinc in the feces was observed in the presence of selenium. The present results indicate an occurrence of clear-cut interaction effects between zinc and selenium administered simultaneously in the rat.     

Effect of zinc and melatonin supplementation on cellular immunity in rats with toxoplasmosis

The effects of zinc (Zn) and/or melatonin supplementation on cellular immunity were investigated in rats infested with Toxoplasma gondii. Fifty Sprague-Dawley male rats were used for this study. All animals were fed a normal diet, ad libitum, containing 97 mg Zn/kg. They were divided into five experimental groups, as follows. Group I (n=10) received intraperitoneal injections of zinc sulfate at a dose of 3 mg/kg/d for 3 wk. Group II (n=10) received intraperitoneal injections of melatonin at a dose of 3 mg/kg/d for 3 wk. Group III (n=10) received intraperitoneal injections of zinc sulfate (3 mg/kg/d) and melatonin (3 mg/kg/d) for 3 wk. Group IV (n=10) was infested controls. Group V (n=10) was healthy controls. There were no differences in the percentage of CD3+ lymphocytes among all groups. For groups I–III, the CD4+ and CD8+ ratios were higher than those of the groups IV and V controls (p<0.01). Similarly, the total lymphocyte ratios in groups I–III were higher than those of infested and healthy controls (p<0.01). The total lymphocyte ratios in group III were significantly higher than those of groups I and II (p<0.01). The plasma Zn levels in the supplemented groups were significantly higher than those of control groups IV and V (p<0.01). These results suggest that melatonin and/or Zn supplementation may activate cellular immunity by stimulating CD4+ and CD8+ production in infected rats with T. gondii.     

Binding of zinc and cadmium to human serum albumin

1. The interaction of zinc and cadmium ion with human serum albumin (HSA) is evaluated and compared by potentiometric titration method and computer simulation of complex equilibria. 2. Zinc binds to histidine and free amino groups, cadmium in addition to basic functional groups of the protein. 3. Whereas zinc binds stronger in 1:1 complexes, chelate binding favours cadmium ions. 4. Within biological pH-conditions, high amounts Zn(II) and even more of Cd(II) will be bound to HSA.     

Effect of supplemental magnesium on the kidney levels of cadmium, zinc, and copper of mice exposed to toxic levels of cadmium

In this report, we present the results of our investigations on the effect of Mg pretreatment on Cd and bioelements (Cu and Zn) contents in kidney of mice exposed to acute and subacute Cd intoxication. Acute intoxication was performed on male Swiss mice given a single oral dose of 20 mg Cd/kg body weight and mice given the same dose of Cd but pretreated with 40 mg Mg/kg body weight. For subacute intoxication one group of mice was given 10 mg Cd/kg body weight every day, for 2 wk, and the other one received the same dose of Cd after oral Mg intake of 20 mg/kg body weight. Cd, Cu, and Zn content was determined in kidney by atomic absorption spectrophotometry. In acute Cd intoxication, Mg pretreatment resulted in significant decrease of Cd in kidney after 4 and 6 h, compared with animals given only Cd. Under the condition of subacute Cd intoxication, Mg supplementation reduced Cd kidney content after 2 wk for about 30%, compared with animals treated with Cd only. The effect of Mg on Cu and Zn kidney content was also beneficial.     

Cadmium tri-tert-butoxysilanethiolates: Structural and spectroscopic models of metal sites in proteins

Syntheses and crystal structures of two molecular, heteroleptic cadmium complexes with CdS₂NO₂ and CdS₂N₂ kernels are described. Bis(tri-tert-butoxysilanethiolate)(1-methylimidazole)cadmium(II) and bis(tri-tert-butoxysilanethiolate)bis(1-methylimidazole)cadmium(II) coexist at equilibrium in chloroform solutions with varying concentrations of bis[bis(tri-tert-butoxysilanethiolate)cadmium(II)] and 1-methylimidazole. The equilibrium is characterized by solution ¹¹³Cd NMR spectra. Solid state CP MAS ¹³C, ²⁹Si, ¹¹³Cd NMR data for the complexes are also reported, analyzed and compared with the results obtained for cadmium-substituted proteins. The similarities and differences between the structures of cadmium complexes and their zinc analogues are discussed.     

Effects of Zinc on Interleukins and Antioxidant Enzyme Values in Psoriasis-Induced Mice

The effects of zinc chloride (ZnCl₂), disodium zinc ethylenediamine tetraacetate (Zn-EDTA), and zinc gluconate (Zn-GLU) on the antioxidant enzyme activities and levels of interleukins (ILs) in psoriasis-induced mice were studied. One hundred twenty female mice were randomly divided into six groups with 20 mice in each group: the control, positive control (PC), methotrexate (MTX), ZnCl₂, Zn-EDTA, and Zn-GLU groups. All animals except the control group were given diethylstilbestrol for three consecutive days. After successfully inducing psoriasis, the control and PC groups were given normal saline (i.g.) daily while the remaining groups were given MTX, ZnCl₂, Zn-EDTA, and Zn-GLU, respectively. The results revealed that the zinc supplementation could significantly (p?<?0.05) inhibit mitosis in the mouse vaginal epithelium as methotrexate did and the inhibiting efficacy had nothing to do with the zinc forms. After ZnCl₂, Zn-EDTA, and Zn-GLU supplementation, the levels of liver superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities increased and the concentration of malondialdehyde (MDA) decreased significantly (p?<?0.05) compared to the PC group. The levels of SOD, CAT activity, and MDA level between each zinc supplementation group and MTX group were insignificant (p?>?0.05). The zinc treatments also caused a significant (p?<?0.05) decrease in the raised IL-2 level of animal serum. The results obtained in the present work indicate the potential for zinc as a complementary pharmaceutical intervention for the treatment of topical psoriasis.     

Metal binding in metallothioneins: Competition for cadmium and zinc between chelex-100 and metal binding sites in metallothionein

A study of the use of the metal chelation properties of Chelex-100 in metal binding reactions of metallothionein (MT), is described. The stoichiometric ratios of bound metals in MT were determined at several stages during a titration in which the Zn(II) in Zn₇MT was displaced by Cd(II), by using Chelex-100 to sequester the free zinc. The stoichiometric ratios provide convincing supporting evidence that the complicated circular dichroism spectral properties observed during the titration arise because the incoming cadmium is distributed across both domains in the protein. It is shown that Chelex-100 does not sequester zinc or cadmium directly from the metallothionein binding sites. Use of Chelex-100 over the temperature range −20 to 65 °C is demonstrated. The chelation capacity of Chelex-100 (in terms of μ metal ion/mg resin) has been determined for a range of elements important in metal toxicology, including: cadmium (33 μ), zinc (22 μ), copper (19 μ), silver (38 μ), lead (40 μ) and mercury (40 μ).     

Effects of cadmium and zinc on the quality of quail's eggs

We report the effects of cadmium (Cd) and zinc (Zn) on the quality of Japanese quail's eggs. For this study, 60 birds were divided into 3 groups of 20 subjects each. The animals in group 1 received 4 mg Zn/d, whereas those in group 2 were given a combination of 4 mg Zn/d and 0.12 mg Cd/d. The quails in group 3 were not given any supplements, acting as controls. The distribution of Cd and Zn in the eggs, the eggs' mass, and the strength and thickness of the shells were determined after 35 and 58 d of supplementation. Zinc showed a positive effect on the mass of eggs and accumulated mainly in the egg white. The content of Cd was significantly lower in the egg yolk of birds in group 1 (p<0.001), whereas those in group 2 had decreased eggshell thickness and strength in comparison to groups 1 and 3 (p<0.001). These results suggest that the adverse effects of Cd on the quality parameters of eggs from commercially important bird species can be, at least in part, counteracted by Zn supplementation.     

Equivalent uptake of organic and inorganic zinc by monkey kidney fibroblasts, human intestinal epithelial cells, or perfused mouse intestine

Zinc (Zn) is recognized as an essential nutrient, and is added as a supplement to animal and human diets. There are claims that zinc methionine (ZnMet) forms a stable complex that is preferentially transported into tissues, and this has contributed to uncertainty about conflicting reports on the bioavailability of various Zn compounds. This study evaluated the cellular and intestinal uptake of inorganic and organic forms of Zn. Steady-state uptake of⁶⁵Zn by human intestine epithelial cells, and monkey kidney fibroblasts was not significantly different with zinc chloride (ZnCl₂), ZnMet, or zinc propionate (ZnProp) (P > 0.05). Uptake of⁶⁵Zn from zinc chelated with EDTA was significantly lower (P < 0.01). In live mice,⁶⁵Zn uptake by perfused intestine and deposition in intestine and liver showed no significant difference between ZnCl₂ and ZnMet. Equimolar [⁶⁵Zn]methionine and zinc[³⁵S]methionine were prepared according to a patented method that yields “ complexed” Zn. Cellular uptake of the radiolabeled methionine was <0.1% of the radiolabeled Zn from these complexes, indicating separate uptake of the Zn and methionine. Gel filtration did not distinguish between⁶⁵Zn in ZnCl₂, ZnProp, or reagent ZnMet, though feed-grade ZnMet containing >10% protein did give a higher-mol-wt form of⁶⁵Zn. Results of this study show equivalent uptake of Zn from inorganic and organic compounds, and support recent feed trials on Zn bioavailability.     

Bioinformatic and Expression Analyses of Genes Mediating Zinc Homeostasis in Nostoc punctiforme

Zinc homeostasis was investigated in Nostoc punctiforme. Cell tolerance to Zn²⁺ over 14 days showed that ZnCl₂ levels above 22 μM significantly reduced cell viability. After 3 days in 22 μM ZnCl₂, ca. 12% of the Zn²⁺ was in an EDTA-resistant component, suggesting an intracellular localization. Zinquin fluorescence was detected within cells exposed to concentrations up to 37 μM relative to 0 μM treatment. Radiolabeled ⁶⁵Zn showed Zn²⁺ uptake increased over a 3-day period, while efflux occurred more rapidly within a 3-h time period. Four putative genes involved in Zn²⁺ uptake and efflux in N. punctiforme were identified: (i) the predicted Co/Zn/Cd cation transporter, putative CDF; (ii) the predicted divalent heavy-metal cation transporter, putative Zip; (iii) the ATPase component and Fe/Zn uptake regulation protein, putative Fur; and (iv) an ABC-type Mn/Zn transport system, putative zinc ZnuC, ZnuABC system component. Quantitative real-time PCR indicated the responsiveness of all four genes to 22 μM ZnCl₂ within 3 h, followed by a reduction to below basal levels after 24 h by putative ZIP, ZnuC, and Fur and a reduction to below basal level after 72 h by putative CDF efflux gene. These results demonstrate differential regulation of zinc transporters over time, indicating a role for them in zinc homeostasis in N. punctiforme.     

Influence of CdCl2 and CdSO4 supplementation on Cd distribution and ligand environment in leaves of the Cd hyperaccumulator Noccaea (Thlaspi) praecox

Background and aims

The aim was to investigate whether different Cd salts in the nutrient solution of the Cd/Zn hyperaccumulator Noccaea (Thlaspi) praecox alter leaf Cd distribution and Cd ligand environment, and plant fitness.

Methods

Plants were grown for 8 weeks with 100/300 μM CdCl₂ or CdSO₄. Leaf biomass, and total chlorophyll, anthocyanin, Cd, Cl, S and P concentrations were monitored. Cd localisation and ligand environment in leaves were analysed using quantitative synchrotron-based micro-X-ray fluorescence imaging, and Cd K-edge X-ray absorption fine structure and Cd L₃-edge micro-X-ray absorption near-edge structure measurements.

Results

Cd uptake and plant fitness were comparable for CdCl₂ and CdSO₄ treatments, and depended on applied Cd concentration. In all treatments, Cd preferentially accumulated with high concentrations of Cl in vacuoles of large vacuolarised epidermal cells, bound mainly to oxygen-based (O)-ligands. In the mesophyll of CdCl₂? treated plants, Cd was preferentially sequestered in vacuoles, while for CdSO₄, Cd accumulated preferentially in the apoplast. In the symplast, O-ligands increased with increasing Cd concentrations; in the apoplast, sulphur-based (S)-ligands prevailed.

Conclusions

Cd partitioning between leaf mesophyll apoplast and symplast and the Cd ligand environment in N. praecox depend on the Cd salt type and concentration added to the nutrient solution.