Chemical Forms Of Cadmium Research Articles

Effects of temperature and chelating agents on cadmium uptake in the American oyster.

Estuarine and coastal waters have increasingly become repositories for the effluents frc~both industrial and agricultural activities. Cadmit~nconcentration in coastal_marine organisms reflect increased concentrations of cadmiumin seawater (MCINTYRE & M/LLS 1975; PHILLIPS 1977; ZAROOGIAN 1976). Although several authors have documented cadmium accululation in oyster (BROOKS & RUMSKY 1967; PRINf~ et al. 1968; SCRUDATO & ESTES 1976; FRAZIER 1976), many questions remain concerning the effects of specific environmental parameters on uptake of cadmium in oyster tissues. The objective of this research was to evaluate the effect of temperature on cadmium accumulations in the tissue of the American oyster, Crassostrea virginica, under controlled laboratory conditions. Oysters have been reported to acc~aalate cadmit~n from seawater containing added cadmium chloride. However, the chemical form of cadmium in seawater has not been defined. This may profoundly influence the mechanism of uptake. Therefore, the present report is also concerned with the effect of chelating agents on the uptake of cadmium. bIATERIALSAND~-THODS Oyster Collection- Single source, adult oysters of similar size (about 3-4 year old) collected from corsrercial fisherman in Deal Island area of Maryland were kept in clean seawater for two days to allow defecation and then brought back to the laboratory. During the two-day period, several gentle cleanings and a final sorting were performed to insure a vigorous group of animals for the experiments. After two weeks of acclimation to the controlled environmental conditions, oysters were used in exposure experiments. Design for Exposure System- Cadmit~n exposure tests were conducted in the laboratory aquaria containing about 50 gal of synthetic seawater which were continuously aerated. The aquaria were equipped with efficient biological filters containing calcite and dolcrnite. Flow rate in each chamber was well controlled. The pH was monitored daily and maintained at 8.1. Toxicant concentrations for cadmium were selected in the range of 40 to 60 ppb. The photoperiod regimen was set according to natural sunlight. The effects of temperature de~ondence on cadmium uptake were^conducted in the range of 5 to 20 C. Salinity was fixed at 15 U/O0.

The chemical form of cadmium in microsomal and mitochondrial fractions from rat liver and kidney after long term administration of cadmium chloride

Wistar rats were given drinking water containing 250 ppm cadmium (Cd) for 12 months. After excising the kidney and liver, the organs were subfractionated into nuclear, mitochondrial, microsomal and cytosol fractions, and the chemical forms of Cd in the subcellular fractions were examined. Although approx. 90% of the total Cd was present in the cytosol, in the form of metallothionein, 3–5% was also present in the mitochondrial fraction and 5–7% in the microsomal fraction from both organs. Each membrane fraction was washed 3 times and there was no contamination of metallothionein from the cytosol according to Cd/protein ratios. By Sephadex G-75 gel filtration, after solubilizing the particulate fractions with sodium deoxycholate, approx. 89% of Cd in the microsomal fraction and 94% in the mitochondrial fraction eluted with the same retention time as that of metallothionein in both liver and kidney, while the remainder was found in a high molecular weight protein fraction. The Cd eluted with the high molecular protein fraction might be involved in dysfunctions in subcellular organelles.

Accumulation and Chemical Form of Cadmium in Lentinus edodes

Because the level of cadmium (Cd) in Lentinus edodes (L. edodes) was the highest among all vegetable foods tested, the accumulation and chemical form of Cd in L. edodes was investigated.1. The mean level of Cd in L. edodes was 0.17ppm (wet basis) and was about six times as high as that in vegetable samples (37 species) tested.2. Among 6 kinds of metals present in woods used for the culture of L. edodes, Cd and zinc (Zn) were concentrated about six and three times in L. edodes cultured on the woods, respectively, whereas the concentration factors of other metals were less than 0.7. L. edodes thus appears to accumulate Cd specifically.3. The distribution of Cd in subcellular components of L. edodes was 45% in the soluble fraction, 26% in the nuclei, 3% in the mitochondria and 3% in microsomes. Cd recovery in this experiment was about 80%.4. Cd in the supernatant obtained by centrifugation of L. edodes homogenate at 16, 000×g for 30 minutes was eluted in Fraction I (Fr-I molecular weight (MW)>ca. 30, 000) and Fraction II (Fr-II MW<ca. 3, 000). The ratio of Cd in Fr-I to Fr-II was approximately 2:1.5. The Cd-binding component in Fr-II had a molecular weight of about 700, gave a positive ninhydrin reaction and had an absorbance maximum at 260nm (pH 8.0). These results suggest that the Cd-binding component of Fr-II is a peptide.

Subcellular Distribution and Chemical Form of Cadmium in Bean Plants

The subcellular distribution and chemical form of Cd in bean plants grown in nutrient solutions containing Cd were investigated. Cd was accumulated mainly in roots and to a minor extent in leaves. Subcellular fractionation of Cd-containing tissues (pH 7.5) showed that more than 70% of the element was localized in the cytoplasmic fraction in roots as well as in leaves. Little Cd (8 to 14%) was bound either to the cell wall fraction or to the organelles. Gel filtration of the soluble fraction showed Cd to be associated mainly with 5,000 to 10,000 molecular weight components in roots, and 700 to 5,000 molecular weight components in leaves. Small amounts of Cd were found in the high molecular weight proteins (molecular weight 150,000). Only traces of Cd could be detected as a free ion. Chemical characterization of the low molecular weight components resulted in the identification of nine amino acids which were identical in roots and leaves. Cd in bean plants is assumed to be bound to peptides and/or proteins of low molecular weight.

Synthesis and Degradation of Metallothionein and Its Relation to the Toxicity of Cadmium

Recent studies on the in vivo synthesis and degradation of matallothionein (MT) were reviewed mainly on the viewpoint of correlations between chemical forms of cadmium in the liver and kidneys and the toxicity of cadmium as follows. i) Analytical methods of MT and general cautions for the procedures which may affect the results of chemical forms. ii) Basal amounts of MT in the liver and kidneys, and their relations to the induction mechanisms. iii) Metal compositions which affect the degradation rate of MT. iv) Synthesis and degradation of MT in the liver after single injection of cadmium, zinc, copper, and endotoxin. v) Chemical forms of cadmium in the liver after repeated injections of cadmium. vi) Degradation and resynthesis of MT in the kidneys after single injection of MT and kidney injury. vii) Changes of chemical forms of cadmium in the kidneys during repeated injections of cadmium and its relation to transitory kidney injury. Transitory kidney injury after single injection of MT and during repeated injections of cadmium were explained as follows : Excess cadmium (than the capacity of basal MT biosynthesis) from the degraded MT for injection of MT or by the accumulation for repeated injections of cadmium cannot be sequestered as MT and causes kidney injury. However, the cadmium induces biosynthesis of MT (transcription of MT mRNA) and, therefore, the restoration occurs despite the constant amount of cadmium or consequtive loadings of cadmium. Persistent kidney injury was supposed to occur when the amount of accumulated cadmium exceeds the capacity of induced MT biosynthesis.

Chemical Forms of Cadmium in Cadmium-polluted Rice. I. Binding Properties of Glutelin-Cadmium Complex

Chemical form of cadmium in rice protein was examined in order to evaluate the toxicological effect of cadmium in rice. 1) Glutelin, one of rice proteins, was purified from commercial rice (Cd 0.10 ppm) and cadmium-polluted rice (2.2-2.5 ppm), resulting in 8 times increase in cadmium content to 0.8-1.2 ppm and 13-20 ppm, respectively. Content of zinc (117 ppm), lead (3.4 ppm), and copper (60 ppm) in the glutelin preparations from cadmium-polluted rice increased, but that of manganese (3.0 ppm) and organic phosphorus (235 ppm) decreased. 2) Glutelin-115mCd complex was prepared from purified glutelin and inorganic 115mCd salt. The cadmium content of the synthetic complex was found to be almost constant in several preparations and remarkably high (2000 ppm). The complex was stable in an alkaline medium but unstable in an acidic medium, dissociating 50% of cadmium at pH 4.0. The complex was stable against heating at 80° for 1 hr. When the complex was dialyzed against various solutions of alkali metal salts, amino acids, and metalchelaters, the complex dissociated 50% in the presence of 3×10-4M EDTA, but stable against alkali metal salts, amino acids, and some other chelaters in a final concentration of 1×10-2M. The complex dissociated completely by the addition of Hg2+ and Cu2+, and partly by the addition of Cd2+, Mg2+, Pb2+, and Zn2+ in the descending order, and was stable against Ca2+, Ba2+, and Mn2+ in a final concentration of 1×10-2M.

Studies on the Distribution and Chemical Form of Cadmium in the Liver of Whelk, Buccinum tenuissimum

In order to clarify the chemical form and role of cadmium in tissues which contain high levels of the metal, the present study was carried out on the subcellular distribution of cadmium and characterization of cadmium-containing protein fraction from watersoluble fraction in the liver of whelk, Buccinum tenuissimum.The concentration of cadmium accumulated by whelk liver was found often more than 1mM and about 30% of which distributed to the 105, 000×g supernatant, about 60% to the nuclear and cellular debris fractions, and residual small amount of the element to the mitochondrial and microsomal fractions.When the liver homogenate was treated with high ionic strength such as 2.0M NaCl and 10mM Na2-EDTA, cadmium content of the soluble fraction increased in both cases by 35% compared with control, which appeared to be explained by ionic adsorption.Cadmium in the soluble fraction did not markedly increase by boiling the liver homogenate for 25min, and also by digestion with proteases; pepsin and trypsin. On the other hand, cadmium in the soluble fraction under the acidic pH, whereat concentration of the metal increased 4-fold compared with that extracted with 0.25M sucrose, was found to be inorganic free state by gel filtration, but under the alkaline pH, cadmium in the soluble fraction almost was found to be bound to proteins.By means of gel filtration over Sephadex G-75, cadmium in the soluble fraction was found to be principally bound to fraction F-I of >75, 000 molecular weight and fraction F-III of <1, 500 molecular weight and a significant amount of cadmium was also associated with fraction F-II of 9, 000 to 13, 000 molecular weight. Under the presence of 2-mercaptoethanol, cadmium in the soluble fraction was almost associated with fraction F-II.Cadmium-binding protein F-I and F-II equilibrated with free cadmium ion, and the equilibrium was influenced with pH and 2-mercaptoethanol. At the acidic pH under pH 5.0, protein bound cadmium decreased sharply, but over pH 7.0, cadmium-protein complex was very stable, and therefore it was difficult to remove completely cadmium from F-I or F-II by dialysis with 1mM Na2-EDTA.These evidences show that cadmium in the liver of whelk are bound firmly to be the nucleus and protein in the soluble fraction.

Chemical Form of Cadmium in Foodstuff. I. Investigation of Chemical Form in Rice Grain

In order to establish a method for toxicological evaluation regarding bio-availability of heavy metals in food, the chemical form of cadmium in rice was investigated. Polishing of the rice can remove only a little of cadmium. In aluron particles separated by the differece of specific gravity from powdered rice, cadmium was located in 3.5-fold higher concentration than other portions, but it was far lower than the degree of concentration of phosphorus, mainly in phytic acid, which is about 65 fold. Cadmium was effectively removed from polished rice grains by only dipping them in acidic medium, but not in neutral and a little in alkaline media. Protein and relatively small portion of phosphorus accompanied cadmium by acidic treatment. On the other hand, diluted sodium chloride solution could also elute cadmium out of rice grains along with phytate-phosphorus. Both effects, acid and salt, look like additive and more than 95% of cadmium was removed from rice grains by several hours of dipping in a mixture of 1% acetic acid and 5% sodium chloride solution. The mode of release of cadmium, protein, and phosphorus under various pH conditions and the subsequent gel filtration of released cadmium fraction reveal that cadmium in rice grains exist as an insoluble complex with phytic acid and protein, which will become soluble, presumably in an inorganic form, in an acidic medium and also become partly soluble under alkaline condition making partly in a high molecular protein-binding form.

Sorption du cadmium par une population de la diatom�e Phaeodactylum tricornutum en culture

The uptake of cadmium by the marine diatom Phaeodactylum tricornutum (Bohlin) maintained in batch culture was measured as a function of successive growth stages of the diatom, and of the chemical form of cadmium in the culture medium (10 μg Cd.l-1). The relative importance of adsorption and absorption of cadmium by the diatom was evaluated. When cadmium was chelated by ethylenediaminetetraacetate (EDTA) the uptake was negligible. In the absence of a chelating agent the uptake varied with the growth phase of the culture, and the major part of the uptake was by adsorption. Two opposite phenomena seen to be responsible for the processes observed: adsorption of cadmium on the cell walls followed by a gradual elution (desorption) by external metabolites.

Cadmium-isocitrate complex: its stability as a function of ionic strength.

The complexation of cadmium by isocitrate has been studied at 25 degrees C and pH 7.5 in a range of ionic strength from 0.01 to 0.16. The formation constant of the complex between cadmium and tribasic isocitrate varies from 860 M-1 at mu=0.16 to approximately 24,500 M-1 at infinite dilution. These data allow the distribution of the chemical forms of cadmium added to the incubation mixtures for tha assay of NAD-dependent isocitrate dehydrogenase to be calculated.