Renal Metallothionein Research Articles

Acute cadmium chloride-induced renal toxicity in the Syrian hamster

It has previously been reported that cadmium (Cd) induces renal lesions only after sequestration by endogenous metallothionein (MT), and not in the form of simple salts. However, in this report we detail findings of acute CdCl 2-induced renal lesions in the Syrian hamster, which appear to be species specific as neither rats nor mice showed such lesions. Adult rats and mice of different strains and Syrian hamsters (Cr:RGH) were given Cd doses ranging from 30–50 μmol/kg, sc, and examined histologically for renal lesions between 2 hr and 7 days later. Hamsters developed necrosis of the proximal renal tubules 12–24 hr after CdCl 2 treatment at an average incidence of 60% in both sexes. Tubular regeneration occurred within 1 week as shown by immunocytochemical localization of DNA synthesis with 5-bromo-2′-deoxyuridine. By electron microscopy, initial changes with Cd (16 hr) included cytoplasmic vesiculation and dilatation of endoplasmic reticulum, and swelling of mitochondria followed rapidly by enlargement of vacuoles, nuclear changes, and cellular disintegration. Rats and mice showed no such lesions even at lethal doses of Cd (40–50 μmol/kg). At maximum tolerated doses of Cd (approximately LD10: for rats and mice, 35 μmol/kg; for hamsters, 50 μmol/kg) renal Cd content was not higher in hamsters than in the other species 24 hr after injection; hamsters, in fact, had the lowest Cd content. Likewise, basal or Cd-induced levels of renal MT were not remarkably different between these species. These results indicate the hamster is uniquely susceptible to acute effects of Cd on the kidney and that this effect is not related to an unusually high concentration of CdCl 2 or unusually low basal or induced levels of MT in the kidney.

Pregnancy-induced mobilization of copper and zinc bound to renal metallothionein in cadmium-loaded rats

Our investigations undertook to examine whether copper (Cu) and zinc (Zn) bound to renal metallothionein (MT) along with cadmium (Cd) in Cd-loaded rats can be mobilized during pregnancy and lactation. Rats of the Wistar strain were injected with Cd. Synthesis of MT containing Cd, Cu and Zn was induced in the kidneys. Concentrations of Cd and essential elements in blood plasma and organs (liver and kidneys) were compared among non-pregnant and pregnant, and Cd-loaded and non-loaded rats at middle and late gestational days and after delivery. Cu bound to renal MT was decreased with gestational age, while Zn was slightly increased. The results indicate that Cu was mobilized and utilized even when the metal was bound to MT in the kidneys of dams. On the other hand, Zn bound to renal MT in Cd-loaded rats was retained and not mobilized during pregnancy. The elution profile of renal MT on an SW column was changed from a typical renal to a mixed profile of renal and hepatic MTs as a result of decreased Cu content in MT. Plasma essential elements changed similarly with gestational age in both concentrations and distributions in non-loaded and Cd-loaded rats. These results indicate that the 3 metals bound to renal MT are dealt with differently during gestation and lactation, and Cu but not Zn is transferred to the fetus, independently of the Cd status of the dam.

Amelioration of the teratogenicity of cadmium by the metallothionein induced by bismuth nitrate.

The participation of maternal hepatic metallothionein (MT) in the amelioration of cadmium teratogenicity in mice was examined. Pretreatment with bismuth nitrate (subcutaneously) ameliorated the teratogenicity, including exencephaly and abnormalities of the axial skeleton, caused by a single intraperitoneal injection of cadmium sulfate. Pretreatment with bismuth nitrate for 3 days induced MT drastically in maternal liver and kidney. Six and 24 hr after the injection of cadmium sulfate, the accumulation of maternal hepatic cadmium increased and that in the decidua, including embryos, decreased after pretreatment with bismuth nitrate. Mouse embryos on day 7 of gestation were cultured for 48 hr. Exposure to cadmium sulfate in vitro induced unfused brain fold, which corresponds to exencephaly in vivo. From the in vitro experiment, it was suggested that the teratogenicity of cadmium on day 7 of gestation is a direct action against the mouse embryo. In the present experiment it was suggested that pretreatment with bismuth nitrate induced maternal hepatic and renal MT; cadmium was therefore trapped and detoxicated, and consequently embryos were exposed to a lower concentration of cadmium.

Pregnancy-associated changes in renal metallothionein concentration and plasma distributions of metals

Pregnancy-associated changes in concentrations and distributions of selected essential elements were examined in the blood and tissues of rats. Concentrations of copper (Cu) and zinc (Zn) in the kidneys of dams significantly decreased with gestational age and revcovered after delivery. Distribution profiles of multi-elements in the supernatant of the kidneys indicated that Cu and Zn bound to metallothionein decreased with gestational age without affecting their distributions to other components. Although concentrations of Cu and Zn in the liver did not show significant changes during gestational period, Zn bound to metallothionein decreased with gestational age. Plasma concentrations of Cu, iron, phosphorus, sulfur, Zn and other elements were altered by the physiological change, some of those chemical forms being assigned.

Elevation in metallothionein messenger RNA in rat tissues after exposure to X-irradiation

Metallothionein (MT) mRNA levels in tissues were measured in rats following whole-body X-irradiation (2 and 20 Gy). When compared with control rats, the elevation in MT mRNA levels of liver, kidney, and thymus was observed in irradiated rats at 9 or 72 hr after irradiation. However, the elevation in MT mRNA levels was not observed in brain, spleen, lung, heart, and testis. When compared with other tissues, testicular MT mRNA levels in control rats were extremely high, and treatment with X-irradiation produced a slight decrease of testicular MT mRNA levels. Time-course experiments indicated that hepatic and renal MT mRNA reached a maximum at 6 hr after irradiation. In lowdose (2 Gy) irradiated rat, these values were returned to control values by 4 days after irradiation. However, in high-dose (20 Gy) irradiated rat, the values were not decreased to control values. These data indicate that treatment with X-irradiation produces an elevation in MT mRNA in rat tissues.

Chelation in metal intoxication XXX: Alpha-mercapto-beta-aryl acrylic acids as antidotes to cadmium toxicity.

alpha-Mercapto-beta-(2-furyl) acrylic acid (MFA), alpha-mercapto-beta-(2-hydroxyphenyl) acrylic acid (MHA), beta-1,2-phenylene di-alpha-mercaptoacrylic acid (1,2-PDMA) and beta-1,4-phenylene di-alpha-mercapto acrylic acid (1,4-PDMA) were compared to sodium N-benzyl-D-glucamine dithiocarbamate (NBG-DTC) an effective cadmium chelator, for their ability to mobilize Cd and influence the Cd induced tissue metallothionein (MT) in rats administered 109CdCl2, 72 hr earlier. MFA was almost as effective as NBG-DTC but more effective than MHA in enhancing urinary and faecal excretion of Cd, reducing tissue and blood levels of Cd and in lowering Cd induced increase in hepatic and renal MT contents. 1,2-PDMA and 1,4-PDMA were effective only in reducing the hepatic burden of Cd. The resuls do not indicate any direct relationship between the efficacy of alpha-mercapto-beta-aryl acrylic acids to decorporate body Cd and their lipophilic-hydrophilic character or number-arrangement of their sulfhydryl groups.

Application of high-performance liquid chromatography--inductively coupled plasma mass spectrometry to the investigation of cadmium speciation in pig kidney following cooking and in vitro gastro-intestinal digestion.

The speciation of cadmium in retail pig kidney has been examined by size-exclusion chromatography (SEC) coupled directly to inductively coupled plasma mass spectrometry (ICP-MS). Approximately 35% of the cadmium from uncooked kidney was soluble after aqueous extraction at pH 8 and SEC - ICP-MS revealed three discrete peaks whose retention times corresponded to estimated relative molecular masses of 1.2 x 10(6), 7.0 x 10(4) and 6 x 10(3)-9 x 10(3). In the cooked kidney, 35% of the Cd was soluble and was all associated with a peak of a relative molecular mass (Mr) of 6 x 10(3)-9 x 10(3). After simulated gastric digestion of cooked pig kidney at pH 2.5, 60% of the cadmium was solubilised and associated with a species of Mr less than 1 x 10(3). When the digest was also subjected to simulated intestinal digestion at pH 6.8, a single peak, which corresponded to 20% of the original cadmium, was eluted. This peak co-eluted with the single peak extracted at pH 8.0 from the cooked kidney. It was also of similar estimated Mr to the single broad peak observed after simulated gastro-intestinal digestion of equine renal metallothionein (Mr = 1.1 x 10(4]. The results suggest that the majority of soluble cadmium in retail pig kidney is associated with a metallothionein-like protein that survives both cooking and simulated in vitro gastro-intestinal digestion.

Effect of age on cadmium-induced metallothionein synthesis in the rat.

Cadmium-induced metallothionein (MT) synthesis was investigated in male rats of three ages, 3, 12 and 24 months. Physiological levels of MT in kidney, liver and lung measured simultaneously in untreated animals were found to be within the same range in all three age groups. Following 3-day treatment with CdCl2 equivalent to 1 mg/kg/day Cd, renal MT increased 10-15-fold in all animals. However, hepatic MT became elevated to 36 times the original value in the youngest (3-month-old) rats and 90 and 74 times, respectively, in the 12- and 24-month-old groups. Lung MT, which responded rather poorly to the cadmium inducer, increased 2-fold in the young group, but about 10 and 8 times, respectively, in the two older groups. High mortality of 75% occurred in the aged (24-month-old) group following cadmium administration, indicating age to be an important sensitizing factor in the toxic hazard of heavy metal exposure. The possible role in this connection of MT is discussed.

The apparent lack of effect of supplementary dietary zinc on zinc metabolism and metallothionein concentrations in the turbot, Scophthalmus maximus (Linnaeus)

Turbot were fed either a basal diet containing approximately 100 mg zinc kg−1 or a similar diet supplemented with 1000 mg kg−1; the fish were sampled over a period of 220 days. At final sampling there was no significant difference between control and test animals in hepatic and renal metallothionein levels, hepatic and renal zinc levels and white muscle, skin and bone zinc concentrations.

Platinum(II) binding to metallothioneins

The reaction of equine renal metallothionein (MT) with excess K 2PtCL 4 at pH 2 results in a polymeric adduct containing 17 ± 2 mol Pt/mol MT. A monomeric adduct containing 7 mol Pt/mol MT is obtained at neutral pH. Rates of reaction of Pt 7MT with DTNB and iodoacetic acid are consistent with Pt 2+ to cysteine thiolate coordination, and the extent of reaction in both cases is 11 ± 2 mol cys/mol MT. Adducts from the reaction of K 2PtCl 4 with apoMT chemically modified at the N-terminal methionine residue, Cd 7MT, and native MT are also reported. A structural model of Pt 7Mt is proposed in which the square planar tetrathiolate Pt(II) unit is incorporated into a three-metal β cluster. Implications for the metabolism of platinum anticancer drugs are discussed.

Developmental and sex differences in cadmium distribution and metallothionein induction and localization.

Age- and sex-related differences in hepatic and renal distribution of cadmium (Cd) and the effect of Cd injection (10 mumol/kg) on tissue zinc (Zn), copper (Cu) and metallothionein (MT) levels were investigated in 2- to 84-day old rats. Renal Cd accumulation increased with age of the animal. Sex differences in renal Cd accumulation were noted in young animals where the 2- and 8-day old males had significantly greater concentration than the females. There were no clear effects of Cd on renal Zn. Renal Cu levels, however, were elevated in the adults. The adult females contained about twice as much MT as the adult males. Cd treatment had no effect on renal MT levels of 8- to 84-day old animals but depressed the levels in 2-day old. Age-related increase in hepatic Cd accumulation was also found; the pattern was more clear cut in females than in males. In addition, in the females the hepatic Cd concentration was significantly higher than in the males. Cd-injection significantly increased hepatic Zn and MT concentrations only in weaned animals. While there were no sex differences in MT levels in the young animals, the weaned females had significantly more MT than the corresponding males. Immunohistochemical staining for MT showed positive staining in both cytoplasm and nuclei of the parenchymal cells. The number of MT-positive nuclei was dependent on the relative MT concentration of the liver. In spite of the intense nuclear staining in 2-day old controls and 84-day old Cd-injected rats, less than 1% of the hepatic MT was present in the nuclear fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of low-level cadmium in rats: Influence of pretreatment with thiol-modulating agents

The effects of low-level cadmium (Cd) administration to rats on animal health, liver and kidney thiols, metallothionein, and glutathione reductase (GSSG reductase) and their modulation by cysteine (as a possible protector) and diethyl maleate (as a possible potentiator) have been investigated. Male Sprague-Dawley rats were treated with sodium or Cd acetate (25 micrograms Cd/kg) orally five times a week for 6 weeks. A second group of animals received cysteine (500 mg/kg; po) before each gavage while a third group received diethyl maleate (DEM) (0.85 mg/kg; ip) in addition to sodium or Cd acetate. When rats were treated with cadmium alone neither weight gain nor serum parameters indicative of hepato- or nephro-toxicity were affected. However, acid-soluble thiols, primarily glutathione, were decreased by about 25% in liver only. A tendency to a decrease in hepatic protein thiols was also noted. No changes were observed for hepatic or renal metallothionein in response to this low level of cadmium administration alone or in combination with the other treatments. Animals receiving cysteine, either alone or with cadmium, showed decreased body weight gain, but no change in serum parameters. Acid-soluble thiols in liver were lower in cysteine-treated rats (24%) and cysteine + Cd (33%) while kidney thiols were unaffected. Administration of DEM alone or with Cd did not cause any alteration in body weight gain. When given DEM + Cd, however, an increase in serum bilirubin was observed, which suggests interference with hepatobiliary function. Acid-soluble thiols were decreased by DEM alone (45%) and DEM + Cd (51%) in liver while renal thiols showed no change. Our data indicate that low-level Cd gavage decreases hepatic cellular thiols but not those of kidney. Cysteine gavage does not protect from the Cd-related effect. Indeed, cysteine itself was found to reduce acid-soluble thiols under the experimental conditions. This was observed only in liver, as was the decrease in thiols due to DEM treatment. DEM administration together with Cd resulted in signs of liver toxicity. There is no indication that inhibition of GSSG reductase by Cd might be involved in the thiol-decreasing effect of short-term repeated low-level gavage of Cd to rats.

Binding of cadmium chloride and Cd-metallothionein to mucosal brush border membrane of the rat small intestinal tract.

Even though Cd is categorized as a metal with low absorption from the gastrointestinal tract, its total body burden predominantly results from its gastric absorption. Oral Cd also eventually triggers an endemic disease, Itai-Itai disease, in certain areas of Japan. Cd absorption is influenced by several endogenous or exogenous factors such as aging, sex, and food components. To resolve the mechanism of Cd absorption from the gastrointesinal tract, metallothionein (MT) is one of the most interesting endogenous substances. Although the protein induced by Cd exists mainly in the mucosal cytosol fraction as well as in those of liver or kidneys, compared to the function of renal or hepatic MT, its function seems to be slightly different. So far, it is reasonable to assume that the protein is involved in the prevention of the transfer of Cd from the mucosa to the body. However, the behavior of MT in/on the mucosal brush border membrane (BBM) is unclear. In order to gain a better understanding of this point, the authors estimated the Cd binding of CdCl/sup 2/ and Cd-Mt to BBM isolated from control and Cd-exposed rats.

Metallothionein Gene Expression in Rats: Tissue-Specific Regulation by Dietary Copper and Zinc

Regulation of metallothionein gene expression by dietary zinc and copper was examined in rat liver, kidney, intestine and brain using a 3 X 3 factorial design. Purified diets containing 5, 30 and 180 mg Zn/kg and 1, 6 and 36 mg Cu/kg were fed for 2 wk. Serum concentrations of copper and zinc were lower at the lowest intakes of either metal than at normal or supplemental levels. Kidney metallothionein levels were proportional to dietary zinc, being 50% less in the 5 mg Zn/kg group than in those fed the highest zinc intake. Metallothionein mRNA was measured by dot blot hybridization to a 32P-labeled oligonucleotide DNA probe representing the terminal 5' sequence of the metallothionein gene. In kidney the number of metallothionein mRNA molecules per cell increased four- to five-fold (from 4 to 29 molecules per cell) with increasing dietary zinc. A less pronounced effect on metallothionein mRNA was observed in response to dietary copper. At the lowest copper intake level and highest intake of zinc intestinal metallothionein mRNA was sevenfold greater than in any other group. Liver and brain did not respond appreciably to the dietary levels of copper and zinc that were fed. Chromatography showed that copper and zinc content of renal metallothionein was directly related to the dietary levels fed. In kidney, both metallothionein-1 and -2 genes were expressed.

Metallothionein metabolism in the liver and kidney of the streptozotocin-diabetic rat

1. 1. Elevated levels of metallothionein (MT)-I and -II were identified in the liver and kidney of insulin-deficient diabetic rats. 2. 2. The relative rate of MT synthesis and the turnover of cytoplasmic MT were both accelerated in the liver of diabetic rats. 3. 3. The rate of synthesis of MT, but not its cytoplasmic turnover, was increased in diabetic kidney. 4. 4. Maximal relative rates of MT synthesis in liver and kidney were first observed at 4 and 10 days, respectively, after inducing the diabetic condition. 5. 5. The altered metabolism of hepatic MT in diabetic rats was attributed primarily to disturbances in endocrine status, while the altered metabolism of renal MT was largely due to accumulation of excessive dietary copper in the kidney.

Kidney synthesizes less metallothionein than liver in response to cadmium chloride and cadmium-metallothionein

Acute exposure to Cd produces liver injury, whereas chronic exposure results in kidney injury. Tolerance to the hepatoxicity is observed during chronic exposure to Cd due to the induction of metallothionein (MT). The nephrotoxicity produced by chronic Cd exposure purportedly results from renal uptake of Cd-metallothionein (CdMT) synthesized in liver. The change in target organ from liver to kidney might be due to a lower amount of MT synthesized in the kidney in response to CdMT. Therefore, the purpose of the present study was to quantitate hepatic and renal MT induced by CdCl 2 and CdMT. MT levels in mice were quantitated using the Cd-heme assay 24 hr after administration of CdCl 2 (0.5 – 3.0 mg Cd/kg) and CdMT (0.1 – 0.5 mg Cd/kg). In both liver and kidney, MT reached higher levels following administration of CdCl 2 (220 and 60 μg/g, respectively) than of CdMT (25 and 35 μg/g, respectively), probably because higher dosages of CdCl 2 than CdMT are tolerated. CdMT produced 19 and 3 μg MT/μg Cd in liver and kidney, respectively, while CdCl 2 produced 11 and 6 μg MT/μg Cd, respectively. In conclusion, induction of MT occurs in both the liver and kidney after administration of CdCl 2 and CdMT. However, the kidney is less responsive than the liver to the induction of MT by both forms of Cd, which may contribute to making the kidney the target organ of toxicity during chronic Cd exposure.

The effect of supplementary dietary copper on copper and metallothionein levels in the fish, dab, Limanda limanda

Abstract Common dab were fed a casein based diet containing copper at a concentration of 1·4 mg copper kg−1 (dry weight) or a similar diet supplemented with 200 mg copper kg−1. Fish were sampled after 10 weeks and 20 weeks and hepatic and renal copper, zinc and metallothionein concentrations were measured. All hepatic cytosolic copper in test and control fish co-eluted from Sephadex G-75 with metallothionein, as did some of the cytosolic zinc. After 20 weeks there was three times as much of this metallothionein-bound copper in the livers of the test fish compared to the control fish, although metallothionein concentration was little elevated. On the basis of these results it is proposed that cytosolic liver copper concentration or heat stable liver copper concentration can be used as an indication of excess dietary copper in the dab Limanda limanda.

Factors affecting hepatic metallothionein levels in marine flatfish

Tissue metallothionein concentrations in marine flatfish have been evaluated as a potential indicator of metal pollution in the sea. The effect on metallothionein in flatfish of agents known to induce its synthesis in mammals was examined. (1) Metals. Intraperitoneal injection of zinc into plaice ( Pleuronectes platessa) gave rise to a rapid and large increase in hepatic metallothionein. This had a half-life of about a month. In contrast, dietary zinc at a concentration of 1000 mg/kg (dry wt) did not significantly increase hepatic nor renal metallothionein levels in the turbot ( Scophthalmus maximus). (2) Stress. There was no effect on hepatic metallothionein in plaice exposed to the stress of capture nor the injection of endotoxin, cortisol, dexamethasone or turpentine. Seasonal variation was found in female plaice. During the breeding season mature fish had occasional very high concentrations of hepatic metallothionein, possibly associated with egg development.

Protective role of renal metallothionein against Cd nephropathy in rats

Rats were treated with four types of Cd compound: CdCl 2, Cd bound to Cys (Cd-Cys), Cd bound to a peptide corresponding to a partial sequence of metallothionein (Cd-peptide), and Cd bound to metallothionein (Cd-MT). This treatment caused no nephropathy. Subsequently, toxic doses of Cd compounds were administered to these pretreated rats and their effects on renal function were examined. When 1.4 mg Cd/kg as Cd-Cys was administered, marked increases in urinary protein, glucose, and amino acid were observed. However, when the animals were pretreated with 1 mg Cd/kg/day as CdCl 2 for 3 days, and 1.4 mg Cd/kg as Cd-Cys was administered 24 hr later, no renal damage was observed. Such a protective effect against the nephrotoxic action of Cd-Cys was also shown by pretreatment with Cd-Cys, Cd-peptide, or Cd-MT. Furthermore such a phenomenon was also observed when the nephropathy was caused by Cd-peptide or Cd-MT. The efficacy of pretreatment depended on the time before subsequent administration of Cd and the dose used for pretreatment. Incorporation of Cd into the liver and the kidney was not altered by the pretreatment. No matter in which form the nephrotoxic dose of Cd was administered, the incorporated Cd was distributed between particulates and cytosol; 3 hr after administration, cytosolic Cd was present in almost equal amounts in the high-molecular-weight and the MT fractions in the nonpretreated rats. However, after pretreatment, more of the Cd subsequently administered was found in the MT fraction. These results suggest that MT participates in the detoxication mechanism against Cd in the kidney, as it does in the liver.

Cadmium, zinc and copper in rabbit kidney metallothionein--relation to kidney toxicity.

Exposure to cadmium results in the production of renal metallothionein (MT) (1–5). In the kidney, MT will bind zinc as well as cadmium (1,2). Studies of renal MT obtained from normal horses, with a comparably high concentration of cadmium in their kidneys, have shown that the relative content of zinc in MT decreases with increasing cadmium concentration in the kidney (4). In rats it has been demonstrated that renal MT may also bind copper (6). It is believed that toxic effects caused by cadmium in the kidney will emerge when the tubular cells are unable to produce enough MT to sequester all cadmium ions (2,7).KeywordsUrinary ExcretionRelative ContentKidney CortexKarolinska InstituteRabbit KidneyThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.