Influence of age on whole-body retention and distribution of 115mCd in the rat

The influence of age on whole-body retention and organ distribution of intraperitoneally applied ^115mCdCl₂ was studied in 1-, 3-, 6-, and 52-week-old rats. The mean percent values of ^115mCd retention in the whole body decreased with increasing age. The distribution of ^115mCd in the body on the 14th day after application shows that in all age groups most of the cadmium is accumulated in the liver (45–56%) and kidneys (4–6%). In younger rats the percentage of cadmium in the kidney and blood was always higher than in older animals in contrast to the liver where it was lower. The percentage of the dose in the liver, kidneys, and blood represents however, a considerably lower fraction of the total whole-body retention in younger animals than in older rats. It is therefore concluded that age bears a significant influence on cadmium metabolism. This might be important for estimating cadmium body burden and critical organ exposure in the youngest age group.     

Inhibition of intestinal calcium uptake by cadmium and the effect of a low calcium diet on cadmium retention

The direct effect of cadium (Cd) on the in vitro uptake of calcium by rat duodenum was examined by incubating mucosal tissue for 1 to 5 min in an isotonic medium containing ⁴⁵Ca with [³H] inulin included to correct for calcium (Ca) uptake associated with the space accessible to inulin. Cadium inhibited a second phase, time-dependent uptake of Ca which is influenced by vitamin D status and dietary levels of calcium. Cadium had no effect on either an initial rapid uptake of Ca (this is complete within one min) or the inulin space of the intestinal mucosa. Kinetic analysis of the Cd inhibition using 1.0 and 3.0 mm Ca against 0.0–1.0 mm Cd demonstrated Cd was a noncompetitive inhibitor with a K_i of 0.8 mm. Alternatively, Ca did not inhibit ^115mCd uptake in animals fed a normal diet. Furthermore, in animals fed a diet low in Ca for seven days, Cd uptake was not affected despite an increased Ca uptake.Whole-body retention and distribution studies of ^115mCd demonstrated that young rats pair-fed a low Ca diet for seven days retained more ^115mCd for nine days from a single oral dose of 100 nmol of CdCl₂ than control animals fed a Ca replete diet. The low Ca diet influenced organ distribution causing more Cd to be retained in the small intestine and kidneys. However, there was no significant change in the sum of the total Cd content in the kidney and liver which are the major sequestering organs of absorbed Cd.     

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.     

Tissue-specific cadmium accumulation, metallothionein induction, and tissue zinc and copper levels during chronic sublethal cadmium exposure in juvenile rainbow trout

Juvenile rainbow trout, on 3% of body weight daily ration, were exposed to 0 (control) or 3 μg/L Cd (as Cd(NO₃)₂· 4H₂O) in moderately hard (140 mg/L as CaCO₃), alkaline (95 mg/L as CaCO₃, pH 8.0) water for 30 days. Particular attention focused on Cd burden in tissues (gills, liver, kidney, and whole body) and induction of metallothionein (MT) in gills, liver, and kidney during chronic Cd exposure. Mortality in Cd-exposed fish was minimal (∼10%), and no growth effects occurred over the 30-day exposure. Cd accumulated in a time-dependent fashion to 9 times (gills), 3 times (liver), 20 times (kidney), 2 times (carcass), and 2 times (whole body) control levels by 30 days; absolute concentrations were in the order kidney > gill > liver > whole body > carcass. Tissue (gills, liver, and kidney) Zn and Cu burdens were not altered by chronic exposure to 3 μg/L Cd. MT concentrations in all tissues increased over the 30 days of Cd exposure, but the increases were much less than those of Cd on a molar binding site basis. Absolute MT concentrations were in the order liver > kidney > gill, but relative increases were greatest in kidney (fourfold), followed by gills (twofold) and liver (1.3-fold). MT levels were sufficient to bind all Cd in gill, liver, and kidney under control conditions, and after chronic Cd exposure remained sufficient in liver and kidney, but not in gills. Total metal levels (Cd + Zn + Cu) greatly exceeded MT binding capacity in all tissues under all conditions. Received: 20 February 2001/Accepted: 20 May 2001     

金属硫蛋白与镉中毒性肝肾损害的关系

目的观察亚慢性镉中毒性肝肾损害,并初步探讨金属硫蛋白（ＭＴ）与肝肾损害的关系。方法用Ｗｉｓｔａｒ大鼠腹腔注射０．５ｍｇ／ｋｇＣｄ２＋的ＣｄＣｌ２３次／周,共１０周,染毒后不同时期处死大鼠,观察肝肾功能变化。结果染毒６周后,大鼠出现了明显的肝肾损害,相应组织中Ｃｄ∶ＭＴ的摩尔数之比均超过７,且随染毒总剂量的增加,Ｃｄ∶ＭＴ值明显增加,病变程度加重。结论肝肾是亚慢性镉中毒的靶器官,非ＭＴ结合的镉可能是损害肝、肾的主要成分。     

重复性注射镉金属硫蛋白诱导小鼠肾脏金属硫蛋白基因的表达

目的　探讨重复性注射镉金属硫蛋白(CdMT)对小鼠肾脏金属硫蛋白(MT)基因表达的影响。方法　以β-actin为内参照,采用半定量RT-PCR方法检测重复性CdMT染毒后小鼠肾脏MT1和MT2基因的表达水平及与染镉剂量和肾皮质镉含量之间的相关性。结果　随着CdMT剂量的增加,MT1、MT2基因的表达水平都相应升高,当CdMT染毒总剂量达到0.60mg/kg时,肾皮质中MT1、MT2基因的表达水平分别为1.60±0.12及1.44±0.05,与相应的对照组(1.22±0.16及0.92±0.12)相比,均明显升高,差异有显著性(P<0.05,P<0.01);肾皮质中MT1及MT2基因表达水平分别与肾皮质中镉的含量呈正相关,其相关系数分别为r=0.72(P<0.01)及r=0.71(P<0.01)。结论　镉对MT1及MT2基因表达具有较强的诱导能力;肾皮质中MT1和MT2基因表达的变化趋势基本相同     

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.     

Trace Elements in Three Marine Birds Breeding on Reunion Island (Western Indian Ocean): Part 2—Factors Influencing Their Detoxification

Seabird tissues collected between 2002 and 2004 from Barau’s Petrel (Pterodroma baraui), Audubon’s Shearwater (Puffinus lherminieri bailloni), and White-Tailed Trop icbird (Phaethon lepturus) colonies on Reunion Island were analyzed for metallothioneins (MTs) and trace element content. The subcellular distribution between soluble and insoluble fractions of Cd, Cu, Fe, Mn, Se, and Zn was determined in liver and kidney. In both, the soluble fraction of the cell concentrated most of the Cd and Se, whereas Fe, Mn, and Zn were preferentially accumulated in the insoluble fraction. The distribution of these elements varied with the tissue, age of the bird, and species. Furthermore, the distributions of Fe and Mn were somewhat influenced by the bird’s physical condition. MT levels were measured in the soluble fraction after heat denaturation. The levels of these proteins varied from 5.5 ± 2.7 mg.g⁻¹ dry weight (dw) to 11.4 ± 6.2 mg.g⁻¹ dw depending on the species and the tissue considered. MT levels were significantly different between liver and kidney only in the White-Tailed Tropicbird. In the three species, MT levels in kidney were significantly higher in adult than juvenile birds. The bird’s weight also had an influence on hepatic and renal MT levels, but not the sex nor the reproductive status. The implication of MTs in Cu and Zn homeostasis and Cd and Hg detoxification are discussed. In addition, clues on Hg regulation by Se were found, especially in Barau’s Petrel, where the levels of these two elements were significantly correlated.     

Characteristics of Adsorption Interactions of Cadmium(II) onto Humin from Peat Soil in Freshwater and Seawater Media

The present study examined Cd solubility in pH 2–12 fresh and seawater media with and without humin to determine Cd species composition. The study, based on the Langmuir–Hinshelwood kinetics model, was conducted to determine the kinetic parameters of Cd(II) adsorption onto humin. We employed the Langmuir and Freundlich models to derive thermodynamic parameters. Aquo (Cd(H₂O) ₆ ²⁺ ) and chloro- (CdCl⁺ and CdCl₂) complexes were responsible for Cd(II) adsorption onto humin. Results showed Cd as Cd(II) and Cd(H₂O) ₆ ⁺² was water soluble at 2 < pH < 7; with a portion of the soluble Cd precipitating as Cd(OH)₂. The Cd(II) rate constant (k) in freshwater was 0.5 × 10^?3 (min^?1), occurring in a single phase, while in seawater fast and slow phase values for k were 31.88 × 10^?3 and 6.2 × 10^?3 (min^?1), respectively. The adsorption curves showed a better fit with the Langmuir than the Freundlich model.     

Effects of subchronic digestive exposure to organic or inorganic cadmium on biomarkers in rat tissues

In an experimental food chain, Wistar rats were fed cadmium (Cd) in an inorganic (CdCl₂) or organic (mainly associated with metallothionein from Helix aspersa snail viscera) form. After 1 month of exposure to 100 μg inorganic Cd g⁻¹ in food, an induction of metallothionein was observed in all target tissues. In liver, glutathione peroxidase (GSH-Px) activity decreased and alanine aminotransferase (ALAT) activity increased, suggesting that Cd causes hepatotoxicity. However, lipid peroxidation as well as catalase and caspase 3 (a marker of apoptosis) activities were not modified. At a rather low exposure (2.5 μg Cd g⁻¹), metallothionein level in the kidney was found to be the most sensitive biomarker of exposure for both Cd forms. In the small intestine of rats ingesting inorganic Cd, metallothionein expression was significantly higher than that observed for rats fed organic Cd. Present results allowed proposing a simple design to assess the effect of a chemical in a trophic transfer approach.     

Effect of the chelating agent sodium tripolyphosphate on cadmium toxicity in mice

The mechanism by which Sodium tripolyphosphate (STPP) increases cadmium toxicity after sc administration was investigated in mice after a dose of Cd (30 μmole/kg), alone or with STPP (90 μmole/kg). The effects of STPP on acute Cd toxicity, development of Cd-induced liver necrosis, rate of Cd transport, distribution of Cd among organs, and Cd binding to metallothionein (MT) was followed. Histological liver changes were not observed during the first 12 hr after injection of Cd, but already 6–8 hr after injection of Cd + STPP early centrilobular necroses and blood stasis appeared. At 12 hr more advanced necroses were present. STPP administered alone was nontoxic and did not change the liver morphology, when compared to animals killed immediately after injection. During the first 12 hr after administration of Cd with STPP there was a much faster transport of Cd giving rise to higher liver and kidney concentrations of Cd and partial inhibition of Cd-MT binding, compared with animals receiving the same dose of Cd without STPP.     

Organ and subcellular distribution of selenium in rats exposed to cadmium,mercury, and selenium

Three groups of rats were given sodium selenite (Se), sodium selenite and cadmium chloride (Se + Cd), or sodium selenite, cadmium chloride, and mercuric chloride (Se + Cd + Hg), respectively. All animals received subcutaneous doses of ¹¹⁵CdCl₂ (0.3 mg Cd/kg) every other day for a fortnight. Mercuric chloride was administered intravenously at doses of 0.5 mg Hg/kg every other day and Na₂⁷⁵SeO₃ intragastrically at doses of 0.1 mg Se/kg every other day for 2 weeks. The whole-body retention of selenium was slightly elevated by cadmium and increased threefold by cadmium with mercury (mainly blood, liver, and kidneys). Cadmium did not affect subcellular levels of selenium in the kidneys and slightly increased the selenium content in the soluble fraction of the liver. On the other hand, combined administration of mercury and cadmium induced a significant elevation of the selenium content in all subcellular fraction of the kidneys and in the nuclear and mitochondrial fractions of the liver. In all animal groups selenium was bound in the soluble fractions of both the liver and kidneys by high-molecular-weight proteins.     

镉对Ⅱ型糖尿病小鼠金属硫蛋白基因表达的诱导与镉肾脏毒性之关系

目的 探讨金属硫蛋白基因诱导表达能力与Ⅱ型糖尿病小鼠（ob/ob小鼠）对镉金属硫蛋白肾脏毒性易感性之间的关系。方法 以β-actin为内参照,采用半定量RT－PCR方法检测在相同肾皮质镉水平条件下,镉对ob/ob小鼠和瘦型小鼠（正常小鼠）肾皮质MT1和MT2基因的诱导表达。结果 镉对ob/ob小鼠肾皮质MT1和MT2基因诱导表达的能力过低,而镉对瘦型小鼠MT1及MT2基因具有明显的诱导能力。结论 本研究提示Ⅱ型糖尿病小鼠对镉肾脏毒性易感的可能原因与糖尿病小鼠肾中镉对MT基因的诱导能力过低有关。     

Gastrointestinal absorption of different compounds of 115m cadmium and the effect of different concentrations in the rat

The absorption and retention of three different compounds of ^115mcadmium and the effects of variations in concentration were studied in female rats. After a single oral dose, the chloride, sulfate, and acetate forms of ^115mCd did not significantly influence the absorption, retention, or distribution of the ^115mCd in the tissues. The only organs containing significant amounts of ^115mCd were the liver, kidney, and gastrointestinal tract. Increases in concentration of cadmium resulted in more cadmium being absorbed from the gastrointestinal tract, although the amount absorbed was not proportional to the increase in concentration.     

Cadmium: Its effects on ovulation,egg transport and pregnancy in the rabbit

The subcutaneous administration of cadmium chloride (CdCl₂) 24 h before hCG-induced ovulation in rabbits sacrificed 14 h after induction of ovulation leads to a dose-dependent decrease in the number of oviductal eggs and the number of eggs shed. While a dose of 1.25 mg/kg CdCl₂ imposed no effect, only 50–67% of the does treated with 2.5 or 5 mg/kg CdCl₂ ovulated and of those ovulated eggs 35.6 and 45%, respectively, were found in the oviducts. At a dose of 7.5 mg/kg CdCl₂, a higher proportion (57.1%) of the does failed to ovulate and only 16% of the eggs were recovered from the oviducts. Ligature of the uterotubal junction failed to increase the rate of eggs recovered from the oviducts. A sharp increase in serum progesterone (Δ⁴p) level within 2 h after induction of ovulation suggeststhat the reduction in the percentage of eggs recovered from the oviducts probably occurred due to altered fimbrial functions. On the other hand, in does treated with 5 mg/kg CdCl₂ 1 or 7 days before mating, pregnancy was interrupted in 60 and 75% of the does together with reduced Δ⁴p concentration and the conception rate (no. of implantations/CL) was significantly reduced. CdCl₂ given 21 days before or 3 days after mating did not affect pregnancy and Δ⁴P concentration remained unaltered. Results suggest that the developing or mature follicles are sensitive to CdCl₂ treatment. Once the CL is formed, the effect of CdCl₂ is reduced. The receptivity of CdCl₂-treated females indicatès that probably the circulating estrogens were not affected and the ability to ovulate in response to hCG and mating reflects that, at least at the doses used, the hypothalamic-pituitary gonads functions are functional in the rabbit.     

Differential protein expression of kidney tissue in the scallop Patinopecten yessoensis under acute cadmium stress

Morphological and proteomic changes in the kidney of scallops exposed to acute cadmium chloride (CdCl₂) were observed, analyzed and compared with those in the non-exposed control group. Under microscopy the paraffin-embedded sections of the kidney revealed that the microstructure of the tissue had been severely deformed after Cd exposure. Two dimensional electrophoresis, MALDI-TOF mass spectrometry and database searches showed 13 differentially expressed protein spots, of which 11 were up-regulated, while two were down-regulated. Among these proteins, guanylate kinase (GK) and C₂H₂-type zinc finger protein are considered to be tightly connected with Cd toxicity. Further studies using quantitative PCR method validated that the GK mRNA was induced under Cd stress. Other proteins identified which had some relevance to Cd toxicity are also discussed. We suggested that differential proteins such as GK could play a potential role as novel biomarkers for monitoring the level of Cd contamination in seawater.     

Metal and Metallothionein Concentrations in Scoter (Melanitta spp.) from the Pacific Northwest of Canada, 1989–1994

Eighty-six surf (Melanitta perspicillata) and nine white winged (M. fusca) scoters were collected from 1989–1994 at 11 locations in British Columbia and the Yukon. Their kidney and liver tissues were analyzed for cadmium (Cd), copper (Cu), zinc (Zn), and metallothionein (MT) concentrations. Individual kidney Cd values ranged from 2.4 μg/g dry weight (DW) in birds from northern Vancouver Island to 390.2 μg/g (DW) in birds from the Queen Charlotte Islands, which is in the range of values potentially associated with kidney damage. Birds from the Queen Charlotte Islands also had high kidney Zn concentrations, which were significantly higher than values in birds from Naniamo and Westham Island on the south coast of BC. Cd values were significantly (p < 0.001) correlated with both Zn and MT concentrations in kidney tissue (r = 0.66 and 0.62, respectively). Male surf scoters had significantly higher kidney Cd and Zn levels than females, with mean Cd values of 47.3 and 19.7 μg/g DW (p < 0.002) for males and females, respectively. Mean Zn values were 120.8 and 108.0 μg/g DW (p < 0.05) for males and females, respectively. However, no sex differences were observed for either Cu or MT concentrations in kidney tissue. Individual MT values ranged from 2.7 to 416.8 μg/g wet weight (WW). Individual kidney Cu values ranged from 15.1 to 48.4 μg/g DW for both sexes. Kidney and liver Cd concentrations were significantly correlated (r = 0.90, p < 0.05) with kidney levels almost always higher than liver values. Although Cd accumulation by the Skidegate scoters was high, comparable tissue Cd values have been documented in other seabirds collected from the same general area, indicating elevated Cd concentrations in marine food chains around the Queen Charlotte Islands (Haida Gwaii) region of the Pacific coast. Received: 17 January 2002/Accepted: 2 June 2002     

Tissue-Specific Cadmium and Metallothionein Levels in Rainbow Trout Chronically Acclimated to Waterborne or Dietary Cadmium

Rainbow trout were exposed to a sublethal concentration of waterborne Cd (0 or 3 g/L) or dietary Cd (0 or 500 mg/kg dry wt) for 30 days to induce acclimation, and tissue Cd and metallothionein (MT) levels were examined. The greatest Cd concentrations were observed in the kidney followed by the gills and liver of the fish exposed to Cd via water, but in the gut tissues followed by the kidney, liver, and gills for dietary-exposed fish, reflecting a variation depending on the route of Cd exposure. Some MT was found in the nonacclimated naïve fish with no experience of elevated Cd exposure, and these background MT levels were quite high in the posterior intestine (480 g/g), cecae (257 g/g), and liver (248 g/g) relative to other tissues (7–50 g/g). With exposure to both waterborne and dietary Cd, MT levels rose significantly in all observed tissues. The increases relative to the control levels of MT in naïve fish were in the order: kidney (5.4 times) > gills (4.6) > liver (1.3) for the waterborne exposure group, and in the order kidney (19.3 times) >> cecae and posterior intestine (6.5 times) > liver and stomach (5 times) > midintestine (4.3 times) > gills (2.1 times) for the dietary exposure group. At 24 hours after an acute gastrointestinal dose of Cd (276 g/kg) infused into the stomach of dietary exposure groups, large increases of total Cd but not MT levels were found in the gut tissues of nonacclimated fish; in the Cd-acclimated fish, the posterior intestine was greatly affected with decreases in Cd (71%), Zn (33%), Cu (70%) and MT (46%) levels, suggesting an enhanced sloughing of tissue materials after infusion. Exposure to Cd did not cause any notable decrease of Zn or Cu in any tissue, except that found in the posterior intestine. However, a molar analysis indicated that although Cd levels remained less than MT binding capacity in both waterborne and dietary exposure groups, the total metal levels (Cd + Zn + Cu) greatly exceeded MT binding capacity in all tissues of Cd-exposed fish, suggesting a potential competition of Cd with other metals for binding sites on MT and non-MT proteins in the tissues.     

Estrogen-Like Effects of Cadmium in Vivo Do Not Appear to be Mediated via the Classical Estrogen Receptor Transcriptional Pathway

Background

Cadmium (Cd), a ubiquitous food contaminant, has been proposed to be an endocrine disruptor by inducing estrogenic responses in vivo. Several in vitro studies suggested that these effects are mediated via estrogen receptors (ERs).

Objective

We performed this study to clarify whether Cd-induced effects in vivo are mediated via classical ER signaling through estrogen responsive element (ERE)-regulated genes or if other signaling pathways are involved.

Methods

We investigated the estrogenic effects of cadmium chloride (CdCl₂) exposure in vivo by applying the Organisation for Economic Co-operation and Development (OECD) rodent uterotrophic bioassay to transgenic ERE-luciferase reporter mice. Immature female mice were injected subcutaneously with CdCl₂ (5, 50, or 500 μg/kg body weight) or with 17α-ethinylestradiol (EE₂) on 3 consecutive days. We examined uterine weight and histology, vaginal opening, body and organ weights, Cd tissue retention, activation of mitogen-activated protein kinase (MAPK) pathways, and ERE-dependent luciferase expression.

Results

CdCl₂ increased the height of the uterine luminal epithelium in a dose-dependent manner without increasing the uterine wet weight, altering the timing of vaginal opening, or affecting the luciferase activity in reproductive or nonreproductive organs. However, we observed changes in the phosphorylation of mouse double minute 2 oncoprotein (Mdm2) and extracellular signal-regulated kinase (Erk1/2) in the liver after CdCl₂ exposure. As we expected, EE₂ advanced vaginal opening and increased uterine epithelial height, uterine wet weight, and luciferase activity in various tissues.

Conclusion

Our data suggest that Cd exposure induces a limited spectrum of estrogenic responses in vivo and that, in certain targets, effects of Cd might not be mediated via classical ER signaling through ERE-regulated genes.