Comparative study of effect of acute administration of cadmium and silver on ceruloplasmin and metallothionein: Involvement of disposition of copper,iron, and zinc

Male ICR mice were subcutaneously injected with either aqueous Ag (1.5 or 5.0 mg/kg) or Cd (1.5 or 2.5 mg/kg) for 2 consecutive days. Body fluids and livers were collected 24 hr after the second dose. In the hepatic supernatant, Ag and Cd were recovered at 2 and 36–46% of the total dose, respectively. Ag-metallothionein (MT), which is associated with Ag, Cu, and Zn, and Cd-MT, which is associated with Cd, Cu, and Zn, were induced in the liver by the injection of Ag and Cd, respectively. The supernatant Ag and Cd existed in the MT fraction at 34–61 and 97% levels, respectively. Cu concentration in the hepatic supernatant was increased by the Ag and Cd injections. The increased Cu was due to the appearance of Ag-MT and Cd-MT, respectively. Microsomal concentrations of Cu increased in the Cd groups, but decreased in the Ag groups. Serum ceruloplasmin (Cp) activity was remarkably increased by the injection of Cd, but severely decreased by the injection of Ag. These opposing changes in Cp activity induced by Cd and Ag may be due not to the sequestering of Cu in MT, but to the alteration of microsomal Cu concentration and/or the difference in affinity of the induction metals to MT. Hepatic Fe concentration was increased by the Ag injection, but was decreased by the Cd injection. These changes may not be related to induction of MT, but to Cp synthesis in the liver.     

Metallothionein Gene Expression in Liver of Rats Exposed to Cadmium and Supplemented with Zinc and Selenium

Cadmium (Cd), one of the most widely distributed heavy metals, is highly toxic to humans and animals. It is well known that zinc (Zn) and selenium (Se) administration reduce the Cd-induced toxicity and that metallothioneins can have a protective effect to mitigate Cd toxicity in biological systems. In this study we report the expression analysis of the two metallothioneines gene classes MT-1 and MT-2 as well as the total metalloprotein content in the liver of rats exposed to Cd (200 ppm), Cd + Zn (200 ppm + 500 ppm), Cd + Se (200 ppm + 0.1 ppm) or Cd + Zn + Se (200 ppm + 500 ppm + 0.1 ppm) in their drinking water for 35 days. Metals accumulation was quantified in rat liver. Cd decreased significantly the hepatic concentrations of Se and increased those of Zn. The treatment of Cd-exposed rats with Se alone or combined with Zn reversed the Cd-induced depletion of Se concentrations in the liver. However, Zn or Zn + Se administration significantly increased the liver Cd uptake and had no effect on the Cd-induced increase in hepatic concentrations of Zn. The molecular assay showed a decreasing trend of MT-1 relative gene expression levels in animals supplemented with Zn (6.87-fold), Se (3.58-fold), and their combination (1.69-fold) when compared to Cd-treated animals (16.22-fold). Upregulation of the MT-2 expression were recorded in all conditions, although fold induction levels were less pronounced than MT-1 expressions. Our data suggest that the well-established protective effect of Zn and Se against Cd-induced toxicity passes through non-MT gene expression mechanisms, being more dependent on the oxidative stress status of the cell.     

Interrelationships between cadmium, zinc and antioxidants in the liver of the rat exposed orally to relatively high doses of cadmium and zinc

Zinc (Zn) reduces cadmium (Cd)-induced toxicity in the liver although it increases Cd tissue burden in some conditions; hence, the present study is designed to study the relationships between Cd, Zn and antioxidants in the liver of rats exposed to Cd. Livers of male rats which received orally relatively high doses of Cd (200 mg Cd/L as Cd chloride or Cd (200 mg/L)+Zn (500 mg Zn as Zn chloride) during five weeks, were investigated. Cd induced an accumulation of Cd and Zn in parallel to depletion in important variables (GSH, GSH/GSSG, CuZn-SOD and GPx activities) and to elevation in others (Cd/Zn and GSSG). Cd, did not affect CuZn SOD/GPx, nor Mn-SOD in the liver. Cd accumulation, Cd/Zn, CuZn SOD activity and CuZn SOD/GPx, was increased remarkably under Zn action. Zn supply ameliorated GSH level and partially reversed the decrease in GSH/GSSG, but it did not ameliorate GPx activity. Analysis showed high correlations between Cd and the majority of the variables, while Zn was positively correlated with only GSSG. We suggest from our results that Zn has indirect ameliorative effects on Cd-induced toxicity in the liver and that the increase in Cd retention is probably the key mechanism modulating, in the case of relatively high doses of Cd, the antioxidant response during exposure to Cd and Zn.     

The relationship of the increased level of metallothionein with heavy metal levels in the tissue of the harbor seal (Phoca vitulina)

The relationship between age, heavy metal levels, and a heavy-metal binding protein, metallothionein (MT), in the liver and kidney of the harbor seal (Phoca vitulina) was studied. The cadmium (Cd) level in the liver and the Cd, inorganic mercury (I-Hg), and zinc (Zn) levels in the kidney were increased with body length, suggesting an age-related accumulation of these metals. The MT levels determined by an MT radioimmunoassay showed concentrations of 240 +/- 139 micrograms/g in the liver and 343 +/- 219 micrograms/g in the kidney. These MT levels were shown to be correlated with age. The statistically significant relationship of the MT levels with the levels of Cd and Zn in the liver and those of Cd, Zn, and I-Hg in the kidney suggested that the protein is responsible for the sequestration of these metals as already observed in terrestrial animals.     

Induction and metal speciation of metallothionein in wood mice (Apodemus sylvaticus) along a metal pollution gradient

We investigated the binding of Cd, Cu, and Zn to metallothionein (MT) and other metal-binding proteins in free-living wood mice (Apodemus sylvaticus L.) captured in four areas along a metal pollution gradient. We measured total and cytosolic Cd, Cu, and Zn concentrations in mouse liver and kidney by means of inductively coupled plasma-mass spectrometry (ICP-MS). Total (Cu, Cd, Zn)-MT levels were determined in the same tissues by means of the cadmium thiomolybdate saturation assay. Metal speciation of metalloproteins was studied by means of size-exclusion high-performance liquid chromatography-ICP-MS. Liver and kidney of wood mice from the site adjacent to the pollution source showed the highest Cd and Zn concentrations (total and cytosolic) and (Cu, Cd, Zn)-MT levels compared to the other sites farther away from the pollution source. No or only small site differences in tissue Cu concentrations were observed. Almost all the variation (85-95%) in hepatic and renal (Cu, Cd, Zn)-MT levels was explained by the total or cytosolic hepatic Zn and Cd concentration or the renal Cd concentration, respectively. An analysis of the cytosolic metal speciation showed that the Cd-MT, Cu-MT, and Zn-MT fractions in liver and kidney increased significantly with increasing cytosolic metal concentrations. Metals associated with the other cytosolic protein fractions did not increase with increasing exposure. These results illustrate the important role of MT in metal homeostasis and detoxification processes. We conclude that MT is a useful biomarker for environmental metal contamination in free-living wood mice.     

锌,硒单独与联合作用对镉毒性拮抗作用的研究

本研究对镉，锌，硒单独或同时给与时相互之间的作用及影响进行了测定，以观察锌，硒对镉毒性的拮抗，实验中把４０只Ｗｉｓｔａｒ大鼠分为镉，镉锌，镉硒，镉锌硒及对照共五组，观察指标为大鼠体重变化；血清，镉，硒，锌；尿：镉，硒，锌；尿蛋白及血清碱性磷酸酶（ＡＫＰ），结果进行统计学处理后表明：加入锌，硒后，镉中毒的大鼠体重回升，血镉下降，尿蛋白下降，血清ＡＫＰ回升，尿镉排出增加，提示锌，硒对镉中毒表现有拮抗作     

Metal-metal interactions of dietary cadmium, copper and zinc in rainbow trout, Oncorhynchus mykiss

The influence of metal-metal interactions on uptake, accumulation, plasma transport and chronic toxicity of dietary Cu, Cd and Zn in rainbow trout (Oncorhynchus mykiss) was explored. Juvenile rainbow trout were fed diets supplemented with (μg/g) 500 Cu, 1000 Zn and 500 Cd singly and as a ternary mixture at 2.5% body weight daily ration for 28 days. Complex interactions among the metals dependent on the tissue/organ, metals ratios and duration of exposure were observed. While Zn did not accumulate, whole-body Cd and Cu concentrations increased following linear and saturation patterns, respectively. Early enhanced whole-body Cu accumulation in fish exposed to the metals mixture was correlated with reduced Cd concentration whereas late enhancement of Cd accumulation corresponded with elevated Cd concentration. This suggests early mutual antagonism and late cooperation between Cd and Cu probably due to interactions at temporally variable metal accumulation sites. At the level of uptake, Cd and Cu were either antagonistic or mutually increased the concentrations of each other depending on the duration of exposure and section of the gut. At the level of transport, enhanced Cd accumulation in plasma was closely correlated with reduced concentrations of both Zn and Cu indicating competitive binding to plasma proteins and/or antagonism at uptake sites. Compared to the Cu alone exposure, Cu concentrations were either lower (gills and carcasses) or higher (liver and kidney) in fish exposed to the metals mixture. On the other hand, Cd accumulation was enhanced in livers and carcasses of fish exposed to the mixture compared to those exposed to Cd alone, while Zn stimulated Cu accumulation in gills. Chronic toxicity was demonstrated by elevated malondialdehyde levels in livers and reduced concentrations of Zn and Cu in plasma. Overall, interactions of Cd, Cu and Zn are not always consistent with the isomorphous competitive binding theory.     

Effect of diet on urinary and fecal excretion of cadmium,copper, and zinc from rats preaccumulated heavily with cadmium

The effects of diets on urinary and fecal excretion of cadmium (Cd), copper (Cu), and zinc (Zn) were examined after loading Cd to a maximum concentration in the livers of rats. The amount of diet and volume of water taken upad libitum by the rats were also traced throughout. The amount of Cd excreted into urine was dramatically increased immediately after changing to a low protein diet, while that excreted into the feces was slightly decreased (not significant). Zn and Cu excreted into the urine were highly and significantly increased in amount by Cd loading but less affected by diets (not significant). However, Zn and Cu excreted into the feces were lowered by the low protein diet due to the low content of the two metals in this diet. Thus, Cd, selectively released from the liver after changing to a low protein diet, was excreted primarily in the urine.     

Cadmium-Resistance Mechanism in the Bacteria Cupriavidus metallidurans CH34 and Pseudomonas putida mt2

Cupriavidus metallidurans CH34 and Pseudomonas putida mt2 were used as cadmium (Cd)-resistant and -sensitive bacteria, respectively, to study Cd uptake, sorption, intracellular accumulation, metallothionein (MT) induction, and bioremediation potential of both isolates. According to this research work, Cd had a stimulatory effect on the growth of CH34 cells (OD₅₇₈ = 1.43) compared with mt2 cells (OD₅₇₈ = 0.8). Addition of N,N′-dicyclohexylcarbodiimide (DCCD) and 2,4-dinitrophenol (DNP) along with Cd resulted in more cell growth in mt2 (OD₅₇₈ = 0.71) compared with CH34 (OD₅₇₈ = 0.34). DCCD and DNP inhibited this active uptake only in CH34 but not in mt2. Greater Cd interaction with the cell surface was observed in mt2 cells compared with CH34 cells. Intracellular Cd accumulation was interrupted by DCCD and DNP in CH34 (only 1.81 ± 0.04 μg L^?1 at 5 h) but not in mt2 (24.41 ± 0.01 μg L^?1 at 5 h). Intracellular Cd uptake was observed in even killed mt2 cells (7.11 ± 0.05 μg L^?1 at 5 h) compared with CH34 cells (2.50 ± 0.08 μg L^?1 at 5 h). This result showed that the Cd accumulation mechanism in CH34 is ATPase-dependent, whereas in mt2 uptake mechanism is not ATPase-dependent because mt2 ATPase was not inhibited by DCCD and DNP. CH34 removed 93 mg L^?1 of Cd after 8 days from original industrial effluent, which was more than Cd removal by CH34 from distilled water (i.e. 90 mg L^?1 after 8 days). mt2 was able to remove 80 mg L^?1 of Cd after 8 days from original industrial effluent, which was more than Cd removal by mt2 from distilled water (i.e. 77 mg L^?1 after 8 days). Cd did not induce any MT in CH34, but it did so in mt2 (14 kDa), which was thought to be a Cd-resistance mechanism operative in mt2.     

Exposure of human proximal tubule cells to cd2+, zn2+, and Cu2+ induces metallothionein protein accumulation but not metallothionein isoform 2 mRNA.

The organization of the human metallothionein (MT) gene family is more complex than the commonly used mouse and rat models. The human MTs are encoded by a family of genes consisting of 10 functional and 7 nonfunctional MT isoforms. One objective of this study was to determine if the accumulation of MT protein in cultures of human proximal tubule (HPT) cells exposed to metals is similar to that expected from the knowledge base obtained from rodent models. To accomplish this objective, HPT cells were exposed to both lethal and sublethal concentrations of Cd2+, Zn2+, Cu2+, Ag2+, Hg2+, and Pb2+ and MT protein levels were determined. The results were in general agreement with animal model studies, although there were some exceptions, mainly in areas where the animal model database was limited. In clear agreement with animal models, Cd2+, Zn2+, and Cu2+ were demonstrated to be potent inducers of MT protein accumulation. In contrast to the similarity in MT protein expression, we obtained evidence that the human renal MT-2 gene has a unique pattern of regulation compared to both animal models and human-derived cell cultures. In the present study, we determined that MT-2A mRNA was not induced by exposure of HPT cells to Cd2+ or the other metals, a finding in contrast to studies in both animal models and other human cell culture systems in which a high level of MT-2 mRNA induction occurs upon exposure to Cd2+ or Zn2+. While MT protein expression may be similar between humans and animal models, this finding provides initial evidence that regulation of the genes underlying MT protein expression may be divergent between species.     

Effect of cadmium on hepatic metallothionein level in early development of the rat

The induction of hepatic metallothionein (MT) was investigated 24 hr after an intraperitoneal injection of 0.75 mg/kg Cd as CdCl₂ · H₂O in rats of 7, 14, 21, and 90 days. Metallothionein in liver cytosolic fractions collected on Sephadex G-75 was characterized in terms of sulfhydryl, total protein, Cd, and Zn contents. Most of the cytosolic Cd was associated with MT and the concentration of Cd was equal in the different age groups. The higher contents of sulfhydryl, protein, and Zn both in control as well as in Cd-injected rats of 7 and 14 days than in those of 21 and 90 days indicate the presence of more native Zn-thionein in immature pups. However, the increase in sulfhydryl and protein contents showed more prominent induction of MT in Cd-exposed animals of 21 and 90 days than in those of 7 and 14 days. The concentration of Cd was highest in liver followed by the other tissues. While hepatic accumulation of Cd was similar in all age groups, the renal accumulation increased significantly with age. The intestine and spleen of immature pups concentrated more Cd than those of mature animals. The accumulation of the metal did not differ significantly in heart and brain of the animals among the four groups.     

Combined effects of methylmercury,lead, and cadmium on hepatic metallothionein and metal concentrations in the pekin duck

This study was initiated to determine the effects of combined treatments of methylmercuric chloride (MeHg), lead acetate (Pb) and cadmium chloride (Cd) administered orally on metallothionein (MT) and metal levels in the liver of the pekin duck (Anas platyrynchos). Methylmercury and Pb induced a two-fold increase in MT while Cd caused a seven-fold increase over controls. Concurrent administration of MeHg and Pb caused no increase in MT over single treatments. The hepatic MT content of the MeHg + Cd and MeHg + Pb + Cd groups was not different from the Cdalone group. Hepatic lead levels were lowest followed by Hg and Cd. Lead increased Hg levels when given simultaneously with MeHg, and further addition of Cd increased this effect. In groups given Pb, MeHg increased hepatic levels of this element, but when MeHg was also given with Cd, the combination produced a reduction in levels of Pb. Lead or MeHg had no effect on Cd levels. Methylmercury, Pb, and their combination elevated hepatic Cu over controls. All treatments significantly raised hepatic Zn levels above controls. Combinations of Cd with either MeHg or Pb lowered Zn levels below that caused by Cd alone. The simultaneous administration of all three metals did not produce Zn levels which were additive. The liver content of iron was not significantly altered.     

发育期胎儿组织中元素的含量分布和意义

对１１８例１６～２４、２５～３２和大于３２ｗｋ的正常胎儿组织颞叶、额叶、顶叶、枕叶、小脑、脑干、延髓、海马，肝脏和股骨肌，母体血清和胎盘用等离子发射光谱（ＩＣＰ）法测定了锌、铁、铜、钙、镁、镉、铬、铝、铅、钠、钾和磷的含量。结果表明，发育期间胎儿组织中元素的含量分布与器官的发育及功能的成熟有关。     

Effect of zinc deficiency on the accumulation of metallothionein and cadmium in the rat liver and kidney

The effects of zinc (Zn) deficiency and repeated exposure to cadmium (Cd) on the accumulation and distribution of metallothionein (MT), Cd and Zn in the liver and kidney were studied. Male Sprague-Dawley rats were fed either a Zn-deficient (1 ppm) or a Zn-adequate (40 ppm) diet during the experiment, and the rats were injected subcutaneously with a cadmium chloride solution (1.0 mg Cd/kg of body weight, 5 days a week) for 4 weeks. Cadmium, Zn, and Cd-induced MT concentrations in the liver and kidney were lower in the Zn-deficient rats (–Zn + Cd) than in the Zn-adequate rats (+ Zn + Cd), while the content of Cd bound to high molecular weight proteins (HMWP) was greater in the Zn-deficient rats (–Zn + Cd). The Zn bound to Cd-induced MT was reduced to 30% in the liver and to 60% in the kidney of the Zn-deficient rats (–Zn + Cd) as compared with that of the Zn-adequate rats (+ Zn + Cd). In the kidney of Zn-deficient rats, exposure to Cd caused a decrease in essential Zn associated with HMWP as compared with that of Zn-adequate rats (+ Zn + Cd). Thus, Zn-deficiency affected the distribution of Cd in tissues, MT and HMWP and accelerated substantially Cd-induced Zn-deficiency in the kidney. Although the renal Cd concentration was lower in the Zn-deficient rats (–Zn + Cd) than in the Zn-adequate rats (+ Zn + Cd), exposure to Cd for four weeks resulted in glucosuria and an increase in liver and kidney weights in the Zn-deficient rats (–Zn + Cd), but not in the Zn-adequate rats (+ Zn + Cd). These results suggest that development of Cd toxicity is related to the Zn status of the body, to the accumulation of Cd in HMWP and to the amount of essential Zn associated with HMWP.