Inorganic Cd Research Articles

Synthesis and Structure of Two Acentric Heterometallic Inorganic–Organic Hybrid Frameworks with Both Nonlinear Optical and Ferroelectric Properties

Solvothermal reactions of Cd(NO3)2·4H2O with aromatic polycarboxylic acids in the presence of sodium nitrate led to two acentric three-dimensional (3D) heterometallic inorganic–organic hybrid frameworks, namely, [Me2NH2][Cd2Na3(2,4-PYDC)4]·2H2O (1) and [Me2NH2] [CdNa(OH-m-BDC)2(H2O)2]·2H2O (2) (2,4-H2PYDC = 2,4-pyridinedicarboxylic acid, OH-m-H2BDC = 5-hydroxyisophthalic acid). The framework of 1 is constructed by a 3D inorganic Cd–Na connectivity, which resembles a concrete reinforcement structure and features a {CdNa}n rod-shaped chain, a {CdNa2}n helical chain, and a 20-membered {Cd6Na14} ring. Compound 2 is built up by one-dimensional inorganic {CdNa}n rod-shaped chains which are further connected by OH-m-BDC2– ligands, affording a 3D polymeric framework. Compounds 1 and 2 crystallize in acentric space groups, and both display powder second harmonic generation efficiencies approximately 0.8 and 0.7 times, respectively, than that of the potassium dihydrogen phosphate (KDP) powder. In addition, they also exhibit luminescence and potential ferroelectric properties.

Using alkaline-earth metal ions to tune structural variations of 1,3,5-benzenetricarboxylate coordination polymers

Alkaline-earth metal ions were used to tune four new heterometallic frameworks, {[Cd(2.07)Mg(0.93)(BTC)(2)(H(2)O)(4)]·2H(2)O}(n) (1), {[Cd(2)Ca(BTC)(2)(H(2)O)(4)]·2H(2)O}(n) (2), {[Cd(2)Sr(BTC)(2)(H(2)O)(5)]·H(2)O}(n) (3) and [Cd(6)Ba(3)(BTC)(3)(H(2)O)(10)](n) (4) (H(3)BTC = 1,3,5-benzenetricarboxylic acid), synthesized from H(3)BTC and the corresponding metal salts. Single-crystal X-ray analysis shows that compound 1 is a three-dimensional (3D) framework based on heterometallic Cd-O-Cd-O-Mg inorganic chain subunits, compounds 2 and 3 are basically isostructural and feature a 3D framework based on Ca(II) or Sr(II) polyhedrons decorated with Cd-O-Cd inorganic chains. Compound 4 is a 3D framework templated by disordered inorganic hydrate Ba(II) ions, and also features inorganic Cd-O-Cd chains, which are connected together through corner sharing with the {Cd(1)O(6)} polyhedrons by {Ba(1)O(6)} polyhedrons, giving rise to a rare heterometallic 3D inorganic skeleton. Moreover, the solid-state fluorescence of compounds 1-4 and NLO properties of compounds 2-4 have also been investigated at room temperature.

Analysis of FDA in-house food reference materials with anticoincidence INAA

In-house reference material (IRM) cocoa powder (CCP) has been in use at US Food and Drug Administration laboratories for about 15 years. A single lot of commercial material was originally characterized for 32 elements by several laboratories and five techniques. A unique approach for basis weight determination based upon ambient relative humidity was developed for CCP, eliminating the need for dry weight determinations. The CCP Reference Sheet is updated by incorporating new results approximately every 5 years. The last update occurred in 2006. As part of an effort to revalidate and update values for CCP, anticoincidence instrumental neutron activation analysis (INAA) was used to determine mass fractions for 16 of the originally characterized elements, as well as to provide information on 16 other elements. Results were in very good agreement with 2006 Reference Sheet values. A new candidate IRM, fresh-frozen swordfish (FFSF) powder, was produced by adding inorganic As, Cd, Cr, Hg, Pb, Sb, and Se to liquid nitrogen-frozen commercial swordfish filets which were then homogenized. Portions of FFSF were analyzed by INAA to provide mass fraction and homogeneity information for As, Cd, Cr, Hg, Sb, and Se as well as for eight other elements occurring naturally in the material. Non-homogeneities were ≤2.5 % for As, Br, Cd, and Cs, and ≤1.8 % for Cr, Hg, Rb, Sb, and Se. Certified reference materials DORM-3 Fish Protein powder and fresh-frozen SRM 1947 Lake Michigan Fish Tissue were analyzed as controls.

THE INFLUENCE OF pH ON ALGAL CELL MEMBRANE PERMEABILITY AND ITS IMPLICATIONS FOR THE UPTAKE OF LIPOPHILIC METAL COMPLEXES(1).

Uptake of lipophilic metal complexes by freshwater algae has recently been shown to be pH dependent. Here we look at different physiological aspects that could influence the diffusion of the lipophilic Cd complex, Cd(diethyldithiocarbamate)2 (0) (Cd(DDC)2 (0) ), into algal cells at different exposure pH values. Changes in cell membrane permeability were assessed as a function of pH for three species of green algae [Chlamydomonas reinhardtii P. A. Dang., Pseudokirchneriella subcapitata (Korshikov) Hindák, and Chlorella fusca var. vacuolata Shihira et R. W. Kraus] using two neutral, nonionic probes, fluorescein diacetate (FDA) and D-sorbitol. In parallel experiments, we exposed algae to inorganic Cd or to Cd(DDC)2 (0) and monitored Cd intracellular metal distribution, together with phytochelatin synthesis. For the three algal species acclimated at pH 5.5 (w/wo DDC 1 μM) and exposed at this pH, their permeability to FDA and D-sorbitol was consistently lower than for algae growing at pH 7.0 and exposed at this pH (P < 0.001). The ratio of the FDA hydrolysis rate measured at pH 7.0 with respect to the rate measured at pH 5.5 (both in the presence of DDC) correlated with the ratio of the Cd(DDC)2 (0) initial internalization rate constant obtained at pH 7.0 versus that obtained at pH 5.5 (three algae species, n = 9, r = 0.85, P = 0.004). Our results strongly suggest that acidification affects metal availability to algae not only by proton inhibition of facilitated metal uptake but also by affecting membrane permeability.

Low Doses of Cadmium Chloride and Methallothionein-1-Bound Cadmium Display Different Accumulation Kinetics and Induce Different Genes in Cells of the Human Nephron

Background/Aims: The present study was conducted to investigate the renal tubular handling of inorganic cadmium (Cd²⁺) by exposing primary human tubular cell cultures to physiologically relevant doses of cadmium chloride (CdCl₂). Furthermore, the cellular accumulation of Cd²⁺ was compared to that of metallothionein-1-bound Cd (Cd7MT-1). Finally, this study aimed to investigate the effect of the accumulation of Cd (both Cd²⁺ and Cd7MT-1) in renal cells on the expression of genes relevant to nephrotoxic processes. Methods: Cd concentration was measured using atomic absorption spectrometry. mRNA expression was evaluated by quantitative real-time RT-PCR. Results: Cd²⁺ accumulated into human tubular cells in a concentration- and time-dependent way. Furthermore, cellular accumulation of Cd²⁺ was different from the cellular accumulation of Cd7MT-1, indicative for different uptake routes. Finally, mRNA expression of the genes encoding the anti-oxidative proteins metallothionein-1 (MT-1) and heme-oxygenase-1 (HO-1) as well as the pro-apoptotic Bcl-2-associated X protein (Bax) were upregulated by CdCl₂ and not by Cd7MT1. Conclusion: In the presence of physiologically relevant Cd concentrations, tubular accumulation of the element in its inorganic form is different from that of Cd7MT-1. Furthermore, the tubular accumulation of inorganic Cd induces mRNA expression of genes of which the protein products may play a role in Cd-associated renal toxicity.

Arylesterase activity in trace element contaminated soils

Arylesterase activity was measured along with microbial biomass C (BC) and respiration, and H2O-soluble and NH4NO3-exchangeable trace elements (TE), in contaminated soils (TECS) from three long-term field trials. The AGIR (AG) soils were contaminated only by inorganic Cd, whereas the Ambarès (AM) and Louis Fargue (LF) soils were contaminated mainly by Mn and Zn, and Cd and Ni, respectively, from past sludge application at different rates. In the AG soils, the arylesterase activity decreased with increasing Cd total concentration and solubility. In the AM soils, the arylesterase activity decreased with increased contamination, whereas in the LF soils the arylesterase activity was increased by sludge additions, with the higher values detected in soils with lower sludge incorporation rates. In the AG and AM soils, arylesterase activity was significantly and negatively correlated with H2O-soluble and NH4NO3-exchangeable TE, whereas in the LF soils it showed a ‘hump’-shaped trend with sludge additions and could not be modelled. Multiple regression analysis showed significant interactions between TE, soil pH value and TOC with this enzyme activity. Respiration values of the AG soils generally increased while the BC generally decreased with Cd contamination, while different trends were observed in the AM and LF soils. No trends in the enzyme activity-to-BC ratios were found in relation to soil contamination. Information regarding the inhibition of arylesterase activity in TECS can be important for the management of soils co-contaminated by TE and organic pollutants, in which the detoxification action of arylesterase may be reduced.

Estrogen-like effects of diet-derived cadmium differ from those of orally administered CdCl 2 in the ERE-luc estrogen reporter mouse model

Cadmium (Cd), an environmental and dietary contaminant, has been described to mimic the effects of 17β-estradiol (E 2) in selected model systems when studied as an inorganic salt. However, inorganic Cd salts do not represent the main form of Cd exposure in general human populations. The aims of this study were to compare the estrogen-like effects and the bioavailability of dietary Cd to inorganic CdCl 2. Adult ovariectomized ERE-luc reporter mice were administered two bread based diets containing different concentrations of Cd (17.57 and 49.22 μg/kg, corresponding to oral intakes of 1.8 and 5.1 μg/kg body weight (bw) per day, respectively), inorganic CdCl 2 (1 μg/kg bw per day by gavage) or E 2 (5 μg/kg bw per day pellet) for 21 days. The effects on estrogen signaling were investigated by studying the uterine weights, luciferase activation, and expression of endogenous estrogen target genes. The uterine weight was significantly increased by both CdCl 2 and E 2 but not by the Cd containing diets. All treatments modulated the expression of luciferase and the endogenous estrogen target genes; however, there was no consistent overlap between the responses triggered by the bread diets and the responses stimulated by CdCl 2 or E 2. Oral exposure to Cd was calculated and the concentrations in liver and kidneys quantified to estimate the amount of absorbed Cd retained in tissues. The results suggest significantly lower absorption and/or tissue retention of dietary Cd compared to CdCl 2 following oral exposure. Altogether, our results support previous reports on in vivo estrogenicity of CdCl 2 but do not suggest the same activity for diet bound Cd. This study calls for caution when extrapolating results from pure compound studies (e.g. estrogenicity of CdCl 2) to dietary exposure scenarios (e.g. estrogenicity of diet bound Cd). Further basic research is needed on the mechanisms of interaction between Cd and the estrogen signaling, biologically active species of Cd, and biomarkers of estrogen-like effects of Cd in vivo before human health risk assessment on the hormone disruptive effects of Cd can be carried out.

Comparative effect of water and food-chain mediated cadmium exposure in rats

This study sets out to compare the absorption and toxicity of Cadmium (Cd) administered via the food-chain and inorganic Cd administered in drinking water after 1 and 3 months exposure using rats as animal model. The food-chain was mimicked by exposing rats to diet containing Cd pre-exposed fish. The uptake of Cd by the rats after both mode of exposure was calculated by summing up the Cd burden in the liver and kidneys and was expressed in terms of % intake. The toxicity of Cd was assessed by monitoring biochemical indices of liver function in the plasma and liver. Regardless of the mode of exposure of the rats, the Cd load in the liver and kidney was significantly (P < 0.05) higher than the respective controls with the kidney having a significantly higher load than the liver after both periods of exposure. However irrespective of the mode of exposure, more Cd was accumulated in the liver and kidney of the 3 months exposed rats relative to those exposed for 1 month. The uptake of Cd by rats exposed to Cd via the food-chain for 1 and 3 months was significantly (P < 0.05) lower when compared to the corresponding water mediated Cd exposed rats, except for the liver after 3 months of exposure. The liver L-ALT activity of rats administered inorganic Cd in drinking water for 1 and 3 months was significantly (P < 0.05) lower as compared to controls. Parallel analysis of the plasma showed no significant (P > 0.05) difference in L-ALT activity between both groups after the same periods of exposure. The L-AST activity in the plasma of rats similarly exposed to Cd for 1 and 3 months was significantly (P < 0.05) higher as compared to controls with a corresponding reduction in the liver. Conversely no significant (P > 0.05) change was observed in plasma and liver L-ALT and L-AST activities after food-chain mediated exposure to Cd for 1 and 3 months in relation to their respective controls. These findings indicate that Cd incorporated in fish is more easily bioavailable, but less toxic relative to inorganic Cd salts at the end of 3 months of exposure in rats.

New Blue‐Light‐Emitting Ultralong [Cd(L)(TeO3)] (L=polyamine) Organic–Inorganic Hybrid Nanofibre Bundles: Their Thermal Stability and Acidic Sensitivity

A new type of blue-light-emitting ultralong [Cd(L)(TeO(3))] (L = ethylenediamine, diethylenetriamine) nanofibre bundle has been synthesised under reflux in a mixed solvent media. Inorganic Cd(TeO(3)) layers are assumed to exist in the structures and are connected by the organic amine molecules through the coordination between nitrogen atoms and cadmium ions. The composition and formulae of these hybrid materials, based on the proposed structures, have been identified through element analysis (EA), thermal gravity analysis (TGA) and energy dispersive spectra (EDS). The thermal stabilities and optical properties of these nanofibre bundles have been investigated. Thermal decomposition of [Cd(en)(TeO(3))] (en = ethylenediamine) and [Cd(DETA)(TeO(3))] (DETA = diethylenetriamine) at 450 degrees C allowed the formation of a mixture of CdTe and Cd(TeO(3)) phases, and a pure CdTe phase, respectively. In addition, this new kind of hybrid bundle, which demonstrates blue emission, was found to be sensitive to acids, and the emission intensity is strongly dependent on the acidity of the solutions, implying that these hybrid nanofibre bundles could be potentially applied as acid sensors.

Role of diet in absorption and toxicity of oral cadmium- A review of literature

The role of diet or its components in the absorption, distribution and toxicity of cadmium (Cd) has received attention in recent times. Experimental evidence in literature strongly suggests that the absorption of Cd is dependent on factors such as age, pH, diet and intestinal metallothionein (MT) production. The chemical forms of Cd such as Cd-MT in foods or inorganic Cd administered directly in foods or drinking water have also been considered in literature. The bioavailability or absorption of Cd as Cd-MT in foods has been shown in many reports to have decreased in relation to Cd administered directly as inorganic Cd in drinking water or foods. However, some other studies have reported contrary findings. Although research evidence has indicated that the type or components of a diet may also influence the absorption or toxicity of Cd irrespective of the chemical form involved. Diets low in proteins, minerals and certain vitamins have been reported to increase Cd absorption and toxicity. Conversely, diets rich in fibres have the reverse effect. The lack of conclusive information on the availability of Cd in Cd-MT for intestinal uptake in relation to that of ionic Cd is noticeable, and as a result there is a great need for further studies in this area. Also, since humans are usually exposed to Cd-MT in foods and rarely to inorganic Cd, the toxicity of food-incorporated Cd deserves further investigation, in view of the observed differences in tissue accumulation from these forms of Cd.

The interaction between inorganic iron and cadmium uptake in the marine diatom Thalassiosira oceanica

We examined substrate‐saturated Fe(II) vs. Fe(III) uptake rates of Thalassiosira oceanica preconditioned to varying degrees of Fe limitation. Inorganic Fe(III) uptake rates by Fe‐sufficient T. oceanica were 2.4‐fold faster than the corresponding inorganic Fe(II) uptake rates. However, when cultures were severely Fe limited, the rate of Fe(II) uptake was upregulated 15‐fold, while that of Fe(III) uptake increased only fivefold. The interactions between substrate‐saturated uptake rates of inorganic Cd(II) and either Fe(II) or Fe(III) by Fe‐limited T. oceanica were also investigated. The addition of equimolar Cd(II) concentration to the Fe(II) uptake media resulted in a ~50% reduction of inorganic Fe(II) uptake rates compared with those in Cd‐free media. In turn, Cd uptake rates were inhibited ~36% in the presence of an equimolar Fe(II) concentration. In contrast to Fe(II), Fe(III) transport exhibited no interaction with Cd(II). T. oceanica thus has separate transporters for inorganic Fe(III) and Fe(II). Cadmium(II) and Fe(II) appear to enter the cell through a common putative divalent metal transporter that is upregulated under Fe deficiency. The interaction of Fe(II) and Cd(II) transport under Fe deficiency provides a plausible mechanism to explain some laboratory and field observations of higher Cd quotas in Fe‐limited phytoplankton.

Comparison of transfer and effects of Cd on rats exposed in a short experimental snail–rat food chain or to CdCl2 dosed food

Transfer and toxic effects of two cadmium (Cd) forms, inorganic (CdCl2 dosed rat food) or organic (contaminated snail-based rat food) were studied in Wistar rat. Cd concentrations in rat food were 0 and 2.5 μg Cd g−1 for both inorganic and organic forms and a high concentration of 100 μg Cd g−1 was also tested for the inorganic form. Rats were exposed for four weeks to contaminated food. Both forms of Cd were bioavailable to rats, with a percentage of transfer from food to rats of around 1% for all contaminated groups. Cd concentrations in rat tissues increased with increasing Cd concentrations in the food. Rats fed with organic form of Cd accumulated significantly more Cd in the main organ for Cd toxicity, the kidney, than those eating the inorganic form. Survival was not affected for any rat group but a decrease in growth and food consumption was observed for the inorganic form. As a defence system against Cd toxicity, rats increased their metallothionein (MT) synthesis at the highest Cd concentration in the target organs (kidney, liver and small intestine) and even did the same at low Cd concentrations (2.5 μg Cd g−1) in the kidney. At this low Cd concentration, MT induction was lower in the small intestine of rats ingesting organic Cd than those ingesting inorganic Cd. Bioavailability of organic and inorganic forms of Cd was similar, but subsequent Cd distribution within organs was different. This quantification of the trophic transfer of both inorganic and organic forms of a toxicant is a basis for a better assessment of the fate and effects of chemicals in food webs.

Different proportions of cadmium occur as Cd‐binding phytochelatin complexes in plants

The aim was to determine cadmium (Cd) speciation in various plants, between buffer-soluble and acid-soluble Cd, and also within the buffer-soluble Cd. A better understanding of Cd speciation shows the relative importance of different biological mechanisms for Cd sequestration. Roots of Pistia stratiodes, Eichhornia crassipes, Agrostis gigantea, Deschampsia caespitosa and wheat Triticum turgidum var. durum were analyzed. Buffer extractions solubilized varying proportions of Cd, ranging from 12% in Eichhornia to 83% in Agrostis. The proportion increased with time of Cd exposure in Pistia. It also increased in wheat roots as the external Cd rose from 0.05 to 0.5 muM and was lowest in old leaves and highest in roots. The remaining Cd was extractable with acid. Gel filtration resolved buffer-soluble Cd into three peaks distinct from inorganic Cd. Two complexes with phytochelatins and related polythiols were present in all cases, inorganic Cd being prominent only in Eichhornia extracts. The phytochelatin complexes accounted for 2% of the root Cd in Eichhornia to 78% in Agrostis. In wheat, phytochelatins bound 82% of the Cd in roots, 19% in young leaves and 12% in old leaves. The cysteine-rich protein metallothionein from wheat was detected immunologically in the void volume of gel filtrations of old and young leaves, but not of roots, and was distinct from the two phytochelatin-based complexes. Speciation of Cd in the various plants indicated that phytochelatins were not necessarily the major ligands of Cd.

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 (CdCl 2) 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.

Selective luminescence detection of cadmium(II) and mercury(II) utilizing sulfur-containing anthraquinone macrocycles (part 2) and formation of an unusual [formula omitted]-crown ether dimer via reduction of Hg(II) by DMF

Sulfur-containing photoinduced charge transfer (PCT) sensors 1,8-anthraquinone-18-dithiacrown-5 ( 2) and 1,8-anthraquinone-18-trithiacrown-5 ( 3) selectively detect both inorganic Cd(II) and Hg(II). Simple heteroatom substitution of the receptor combined with an integrated intraannular carbonyl oxygen fine-tunes selectivity by simple synthetic design. In addition, the high yield synthesis of mercurous ion, Hg 2 2 + , has also been observed via the reduction of Hg(II) in the solvent dimethylformamide (DMF), which has not been previously reported. Spectroscopic and X-ray crystallographic results for Cd 2+, Hg 2 2 + and Mg 2+ complexes of oxygen and sulfur-containing derivatives of 1,8-anthraquinone-18-crown-5 are presented.

Influence of smoking on metallothionein level and other proteins binding essential metals in human milk

To assess the influence of smoking on the level of total protein, metallothionein (MT), albumin and lactoferrin in human breast milk. Samples of whole milk and supernatants of milk after centrifugation at 10 000 x g and 105 000 x g were analysed. Cadmium was determined by graphite furnace atomic absorption spectrometry (GFAAS). The concentration measurements employed the following methods: total protein by Lowry, albumin by colorimetry, cotinine and lactoferrin by ELISA tests, metallothionein by 109Cd/haemoglobin assay. The assessment of tobacco smoke exposure was based on concentrations of cotinine in breast milk (197 +/- 98 ng/ml in smokers and 23 +/- 11 ng/ml in non-smokers; p < or = 0.001) and serum (179 +/- 87 ng/ml and 32 +/- 19 ng/ml, respectively; p < or = 0.001). The level of cadmium was four times higher in the milk of smoking women than in non-smokers. The concentration of total protein was lower in smoking (37.3 +/- 10.6 mg/ml) than in non-smoking mothers (51.8 +/- 13.8 mg/ml; p < or = 0.02). No significant differences between albumin and lactoferrin concentrations were observed. The level of metallothionein was over twice as low in smokers (5.1 +/- 1.9 microg/ml) than in non-smokers (13.4 +/- 3.0 microg/ml; p < or = 0.001), and an inverse correlation between MT level and cadmium concentration (r = -0.86; p = 0.001) was noticed. The breast milk of smoking mothers might be of lower nutritive value. The amount of MT transported by milk to the mammary gland is smaller in smokers than in non-smokers, which may prove to be advantageous to an infant because of the higher toxicity of the Cd-MT complex than that of inorganic Cd salts.

Syntheses, structures and properties of three metal pyridinecarboxylates

Three new metal pyridinecarboxylates, namely [Co 2(pydc) 2(H 2O) 5] ( 1), [Mn(pydc)(H 2O) 2] ( 2) and [Cd 2(OH) 2(2,4-pydc)] ( 3), were hydrothermally synthesized. X-ray single crystal structural analysis revealed: 1 and 2 have polymeric one-dimensional chain-like structure constructed by dinuclear cobalt units and Mn–O chains, respectively; 3 has a three-dimensional layer pillared structure constructed from inorganic Cd–O layer and pydc pillars. 1 shows antiferromagnetic interaction but 2 shows alternative antiferromagnetic and ferromagnetic interactions.

Effects of cadmium in herbage on the apparent absorption of elements by sheep in comparison with inorganic cadmium added to their diet

A meta-analysis of existing scientific literature recently suggested that Cd is absorbed more efficiently by sheep if it is in the organic form in grass, than if it is added as an inorganic supplement to the diet. We tested this experimentally by feeding sheep grass from contaminated soil, compared with uncontaminated grass and with Cd added to the diet. To produce contaminated herbage, Cd nitrate was added to soil in 11 lysimeters sown with perennial ryegrass, with a further 11 lysimeters receiving no Cd to produce uncontaminated herbage. In the Cd-treated lysimeters, soil had increased exchangeable K, Mg, and Ca, leachate had increased K, Mg, Ca, Na, and P, grass had increased Cd and reduced Mg, Na, P, Mn, Fe, Cr, Al, and Ni, and there was some reduction in grass yield compared with untreated lysimeters. Grass from Cd-treated or untreated lysimeters was fed to groups of 12 ewes for 2 days, with Cd intake equated by adding Cd nitrate to the concentrate feed of ewes receiving the uncontaminated grass. The apparent absorption of Cd, Zn, Mo, Cr, and Al was increased for ewes receiving Cd-enriched grass, and apparent absorption of Cu was reduced, compared to those receiving supplementary inorganic Cd. Most of the unabsorbed Cd was excreted in feces within 4 days of feeding. The ewes consuming Cd in grass had increased B concentrations in their urine, possibly due to adverse effects of Cd on kidney function. Finally, the ewes were offered a choice of the two herbages and they ate significantly more of the uncontaminated grass. It is concluded that the apparent absorption of Cd and other heavy metals by sheep in a short-term experiment was greater when Cd was in the grass than when the Cd was added in in an inorganic form and that sheep partially avoided herbage with a high Cd concentration.

Cadmium uptake in rat hepatocytes in relation to speciation and to complexation with metallothionein and albumin.

Cadmium (Cd) uptake has been studied in primary cultures of rat hepatocytes focusing on the impact of inorganic and organic speciation. Uptake time-course studies over a 60-min exposure to 0.3 microM (109)Cd revealed a zero-time uptake and a slower process of accumulation which proceeds within minutes. (109)Cd uptake showed saturation kinetics (K(m) = 3.5 +/- 0.8 microM), and was highly sensitive to inhibition by Zn and Hg. There was no evidence for sensitivity to the external pH nor for any preferential transport of the free cation Cd(2+) over CdCl(n) (2-n) chloro-complexes. According to the assumption that only inorganic metal species are available, metal uptake decreased upon albumin (BSA) addition to the exposure media. In contrast, higher levels of (109)Cd accumulation were obtained under optimal conditions for Cd complexation by MT. Comparison among uptake data obtained under inorganic and organic conditions revealed that Cd-MT would be taken up 0.4 times as rapidly as Cd(inorg). We conclude that uptake of Cd in rat hepatocytes involves specific transport mechanism(s) subjected to Zn or Hg interactions. Uptake of inorganic Cd is not proportional to the levels of free Cd(2+) and does not involve the divalent cation transporter DCT1 nor the co-transporter Fe(2+)-H(+) NRAMP2. We found Cd-MT but not Cd-BSA to be available for the liver cells, and have estimated a binding affinity four orders of magnitude higher for Cd complexation with MT compared to BSA; MT may have a significant role in Cd delivery to the liver.

Effects of ingestion of cadmium-polluted rice or low-dose cadmium-supplemented diet on the endogenous metal balance in female rats.

The concentrations of endogenous metal ions in liver, kidney, and bone tissues of female rats were measured after ingestion of cadmium-polluted rice (1.24 ppm as Cd) or cadmium-supplemented rice (1.24 and 4.96 ppm) for 2 or 4 mo. The metal accumulated mainly in the kidneys and in the liver. The concentration of cadmium (Cd) in the kidneys of rats fed a 1.24-ppm Cd-supplemented diet was significantly higher than in the Cd-polluted rice group. After 2 mo, the levels of iron and sodium in the liver were elevated in the Cd-polluted rice group, but not in the 1.24-ppm Cd-supplemented group, as compared to controls. The zinc concentration in the Cd-polluted rice group was decreased. The concentration of copper in the kidneys was increased for all Cd-containing diet groups. After 4 mo, the effects of Cd on essential metals in the Cd-polluted and 1.24-ppm Cd-supplemented groups had almost disappeared, although several metal ions in selected organs in the 4.96-ppm Cd-supplemented group showed more prominent changes than in the group exposed for 2 mo. These results suggest that the effects of short-term exposure to Cd on essential metal balance are stronger for rice-bound Cd than for inorganic Cd, although the absorption rate of Cd in Cd-polluted rice may be lower than that of cadmium chloride added to rice.