Effect of cadmium administration and aging on the concentration of essential metals in liver and kidney

To investigate the changes in the concentration of essential metals in organs caused by exposure to cadmium (Cd) and by aging, Cd was administered subcutaneously in single doses of 0.3, 0.9 and 2.7 nig/kg to female rats 10 and 40 weeks of age. The animals were sacrificed on the 7th day after the administration. The concentration of Cd, zinc (Zn), copper (Cu), iron (Fe) and manganese (Mn) in the liver and the kidney was determined and the relations between the concentration of Cd and that of other metals were investigated.1) In 10-week-old rats, the amount of Cd accumulated in the liver and the kidney increased linearly with increasing doses of Cd, while in 40-week-old rats, suppressed accumulation of Cd in the liver and increased accumulation of Cd in the kidney were found after administration of the high dose.2) The concentration of Zn in the liver and the kidney both increased with increasing doses of Cd. There was no age-related difference.3) The concentration of Cu in the liver increased in the animals which received the intermediate and the high dose, irrespective of age. The concentration of Cu in the kidney showed no changes caused by Cd administration or by aging.4) The concentration of Fe in the liver increased in both 10-week-old and 40-week-old rats which received the high dose. The concentration was higher in 40-week-old rats than in 10-week-old rats. The Fe concentration in the kidney and the Mn concentration in the liver and the kidney was not affected by Cd administration or by aging.5) Discriminant analysis, by age, suggested that the amount of metals in the liver and the kidney was more likely to be affected by exposure to Cd in young individuals and less likely to be affected by exposure to Cd with the increase of age.     

Dietary assimilation and elimination of Cd, Se, and Zn by Daphnia magna at different metal concentrations

This study examines the influences of Cd, Se, and Zn concentrations in ambient water on the assimilation, elimination, and release budget of metals, and the clearance rate of Daphnia magna through ingestion of phytoplankton diets. With increasing ambient metal concentration over two to three orders of magnitude, the assimilation efficiencies (AEs) of Cd and Se from two green algal species, Scenedesmus obliquus and Chlamydomonas reinhardtii, decreased significantly. In contrast, the Zn AE from ingested food, which typically was low (<7%), was not impacted by the difference in Zn or Cd concentrations in ingested cells. The Cd AE also was reduced significantly by a high Zn concentration in ingested algae, perhaps due to the competitive assimilation between the two metals. Metal elimination was determined after the daphnids were exposed to the radiolabeled diets for 3 d. The elimination rate constant was not dependent on the metal concentration in ingested food. Similarly, the routes of metal elimination (excretion, egestion, molting, and neonate production) were less influenced by the metal concentration. The rapid elimination of Se and Zn may be attributed to the transfer of these metals from mother to offspring. Except at the highest Cd (917 nM) and Se (1,333 nM) concentrations, there was no significant effect of metal concentration on the clearance rate of the animals. Consequently, the metal assimilation in D. magna may play an important role in the regulation of Cd and Se influx into the animals, whereas the regulation of the metal tissue burden in the animals is unlikely to be achieved through the metal elimination. The trophic transfer factors (TTF) of Cd and Se were related inversely to the metal concentration in the water, whereas the TTF of Zn was less variable at different Zn concentrations. The change of TTF with metal concentration will have important implication for ecotoxicity testing using D. magna, especially when the dietary exposure is incorporated.     

Effects of humic acid and competing cations on metal uptake by Lolium perenne

Within the biotic ligand model, which describes relationships between chemical speciation and metal binding at an organism's surface, multicomponent (long-term) metal uptake by plants has seldom been studied. In the present work, we exposed perennial ryegrass to nutrient solutions with two levels of Cd, Cu, Ni, Pb, and Zn (1 and 0.1 microM) and with or without 30 mg/L of humic acid. Iron and Mn concentrations were constant over all treatments. The hypothesis tested was that humic acid lowers the free and labile metal concentration and, therefore, reduces the metal uptake and, finally, the metal content of the plant. The free metal ion concentrations in the nutrient solutions were measured by the Donnan membrane technique and labile metal concentrations by diffusive gradients in thin-films. The metal content of the shoots depends on the metal content of the roots. The metal content of the roots is a function of the adsorption of metals on the root surface. In a multicomponent system at metal concentrations of 1 microM, humic acid decreased Cu, Pb, and Fe adsorption at the root surface, but it increased Cd, Zn, and Mn adsorption at the root surface. Complexation of cations such as Cu, Pb, and Fe with high affinity for (dissolved) organic matter may lead to increased uptake of cations with low affinity for organic matter (Ni, Zn, and Cd) because of competition between cations at the root surface. The results suggest that competition between metal ions can play a major role in multicomponent metal uptake, which has to be taken into account during risk assessments of metal-polluted soils.     

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

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

Interclonal variation of heavy metal interactions in Salix viminalis

In the complex chemistry of soil, interactions between metals can be expected and these affect the uptake of the metals by the plants. The role of the metal-metal interaction may vary between different plants. This study was performed to investigate if variations exist in the interactions between Cd, Cu, and Zn on toxicity and accumulation of these metals in different clones of Salix viminalis. Two studies were performed. First, to study interaction at uptake, 10 clones with high or low accumulation capacity of Cd, Cu, and Zn, respectively, were treated with 0.3 microM Cd, 0.1 microM Cu, and 3 microM Zn (all three metals at the same time or separately). Second, to study the effect of one of the metals on the sensitivity of the plant to the other metals, three clones with high or low sensitivity to each of the three metals were used in a modified Weibull analysis. Examination of the results shows that interclonal variation exists in effects of metal interaction on metal accumulation and sensitivity exists. The uptake experiment showed that accumulation of Cu was decreased by the other metals, but only in clones with high Cu-accumulating properties because of decreased net uptake of Cu. The accumulation of Zn in roots was increased two- to threefold in all clones in the presence of the other metals because of a decreased translocation of Zn to the shoot. The accumulation of Cd was not changed by the presence of the other metals in any of the clones. The second experiment showed that the effect of interactions between the different metals on metal toxicity was present in all clones but appeared most frequently in the clone with high Zn resistance. Synergistic effects between Cu and Zn in the Zn-resistant clone suggested that this clone had evolved an additional site of toxic action that was absent in the other clones.     

Effects of industrial metals on wild fish populations along a metal contamination gradient

The purpose of this study was to examine relationships among water, sediment, and fish tissue metal concentrations as they relate to fish diversity, tissue metal accumulation, and fish morphometric and reproductive condition. Fish were captured in 12 lakes near Sudbury, Ontario, Canada, that ranged in their degree of metal contamination. In general, metal concentrations in water and sediment decreased with increasing distance from industrial operations. However, only Cu and Ni demonstrated this trend in sediments. Although 20 fish species were identified in the 12 lakes, only one species, yellow perch (Perca flavescens), was common to all 12 lakes. Fish diversity was only associated with sediment metals, suggesting that short-term processes are much less important than long-term processes for fish community recovery in metal-contaminated lakes. Multivariate characterization of water metal concentrations resulted in three lake clusters: Group 1 consisted of reference lakes; Group 2 lakes had high alkalinity, conductivity, hardness, pH, waterborne metals (especially Se), and sediment Cu and Ni concentrations; Group 3 lakes had high pH, waterborne and sediment Cu, and sediment Ni, intermediate alkalinity, conductivity, and waterborne metals (except Al and Fe), and low hardness and waterborne Al and Fe. Liver Cd, Cu, Ni, Pb, and Zn, muscle Zn, and intestinal Cd and Zn were highest, and muscle Cu and male gonadosomatic index (GSI) were lowest, in Group 3 fish. Liver, muscle, and intestinal Se concentrations, and Fulton's condition factor (FCF), hepatosomatic index (HSI), and male GSI were highest in Group 2 fish. Group 1 fish had the highest muscle Hg concentrations and female GSI. Muscle Se appeared to have an antagonistic effect on muscle Hg accumulation as a function of distance from smelting operations. Neither Cu nor Ni, both metals of concern in the Sudbury area, was useful for predicting fish condition, probably because of homeostatic regulatory control. Liver Cd accumulation, which was negatively related to FCF (r = -0.16; P < 0.05), exhibited strong, nonlinear inhibition (r2 = 0.99; P < 0.0001) as a function of water hardness. Because Cd was not detected in water samples in this study, we suspect that branchial Ca2+ uptake may play some role in reducing dietary Cd uptake in hard water lakes. Selenium has received relatively little attention in the contaminated systems around Sudbury, yet our results demonstrated that tissue Se was related to all condition metrics studied. Moreover, evidence was provided that suggests that there is a gender-specific interaction between dietary Se and Cu uptake that may contribute to decreased female reproductive condition in wild yellow perch.     

Prediction of metal bioavailability in Dutch field soils for the oligochaete Enchytraeus crypticus.

Current risk assessment procedures ignore that variation in soil properties results in substantial differences for uptake and effects in organisms in different soils. In this contribution is presented the results of a study on the soil-related factors that modulate metal uptake and elimination by the oligochaete worm Enchytraeus crypticus. Uptake of Cd, Cu, Pb, and Zn was quantified in 20 Dutch field soils as a function of time. Uptake rate constants and equilibrium concentrations were estimated using compartment modeling. Internal metal concentrations varied less than the corresponding external levels. Zn and especially Cu provided the most extreme examples of this general behavior, which suggests regulation by the organism. Body residues by Cd increased linearly over time in 11 of the 20 soils studied, whereas in the remaining 9 soils equilibration of internal Cd levels was observed. CaCl2 extraction could be used to discriminate the 9 soils in which there is Pb accumulation from the 11 soils in which bioavailable Pb levels were too low to allow for uptake. Multivariate expressions that describe uptake rate constants and bioaccumulation factors as a function of soil characteristics were derived. pH and cation exchange capacity were the most important parameters. The formulae were very similar to those describing partitioning of metals over the solid and liquid phase of the soils, which suggests pore water-mediated uptake. A semi-mechanistic approach yielded further evidence of pore water-related uptake, modulated by competition between H+ and metal ions at the active sites of the membranes.     

Toxicity of eight metals to Malaysian freshwater midge larvae Chironomus javanus (Diptera, Chironomidae)

Fourth instars larvae of freshwater midge Chironomus javanus (Diptera, Chironomidae) were exposed for a 4-day period in laboratory conditions to a range of copper (Cu), cadmium (Cd), zinc (Zn), lead (Pb), nickel (Ni), iron (Fe), aluminium (Al) and manganese (Mn) concentrations. Mortality was assessed and median lethal concentrations (LC(50)) were calculated. LC(50) increased with the decrease in mean exposure times, for all metals. LC(50)s for 96 hours for Cu, Cd, Zn, Pb, Ni, Fe, Al and Mn were 0.17, 0.06, 5.57, 0.72, 5.32, 0.62, 1.43 and 5.27 mg/L, respectively. Metals bioconcentration in C. javanus increases with exposure to increasing concentrations and Cd was the most toxic to C. javanus, followed by Cu, Fe, Pb, Al, Mn, Zn and Ni (Cd > Cu > Fe > Pb > Al > Mn > Zn > Ni). Comparison of LC(50) values for metals for this species with those for other freshwater midges reveals that C. javanus is equally or more sensitive to metals than most other tested dipteran.     

A kinetic model for the relative contribution of waterborne and dietary cadmium and zinc in the common carp (Cyprinus carpio)

In this work, the uptake and whole-body accumulation of Cd and Zn by the common carp from water, diet, and a combination of both was studied using the radioactive tracers 09Cd and 65Zn. A three-compartment pharmacokinetic model was constructed and revealed metal- and exposure route-dependent accumulation profiles. Under the tested exposure conditions in water (0.1 microM Cd and 1 microM Zn), only 0.1 and 0.07%, respectively, of the total Cd and Zn load that passed the branchial surfaces was accumulated by the carp. In contrast, the carp accumulated 20 and 29% of the total ingested Cd and Zn load (mean concentrations in food of newly accumulated metals were 2.24 +/- 0.29 and 19.91 +/- 2.89 nmol/g wet weight, respectively). However, the contribution of the waterborne metals to the whole-body metal accumulation was higher than the metal uptake from food. The constructed model was used to simulate the effect of variable assimilation efficiency (AE) values on the relative importance of dietary Cd and Zn exposure to the overall metal accumulation in common carp. This simulation was performed under a realistic exposure scenario and with Cd and Zn AE values ranging from 5 to 95%. Dissolved Zn levels were higher and Cd levels lower compared to the laboratory experiments. Levels in the midge larvae were much higher. The results show that under these conditions, even at the lowest Cd and Zn AEs, almost 40% of the total body Cd and Zn concentrations originated from dietary Cd and Zn exposure. Taking into account the Cd and Zn AE of the laboratory experiments, respectively, 31 and 55%, more than 85% of the total body Cd and Zn was taken up from the food.     

Allometry of heavy metal bioconcentration in the echinoid Paracentrotus lividus

The relationships between concentration and size in Paracentrotus lividus were studied for seven metals (Zn, Pb, Cd, Fe, Cr, Cu, and Ti). In the calcified body compartment, Zn concentrations showed inverse power relationships, while concentrations of Pb, Cd, and Cr increased as power functions of echinoid size; Fe, Cu, and Ti concentrations did not vary significantly with echinoid size. In the non-calcified body compartment of the echinoid, the concentrations of Zn, Pb, Fe, Cu, and Ti showed inverse power relationships, Cd concentrations increased linearly, and Cr concentrations did not show any significant relationship with echinoid body size. Most relationships were rather weak, except in the cases of Pb and Fe in the non-calcified compartment and Cd in the calcified compartment. The allometric relationships were affected by seasonal factor in the non-calcified compartment only. The results indicate that biomonitoring programs using P. lividus as an indicator of metal contamination must take into account both echinoid size and season as source of metal concentration variations.     

Relating environmental availability to bioavailability: soil-type-dependent metal accumulation in the oligochaete Eisenia andrei

Body residues are often better estimates of the amount of a chemical at the sites of toxic action in an organism than ambient soil concentrations, because bioavailability differences among soils are explicitly taken into account in considerations of body residues. Often, however, insufficient attention is paid to the rate and extent at which tissue concentrations respond to soil concentrations and soil characteristics. In this contribution the impact of soil characteristics on the environmental bioavailability of heavy metals for the oligochaete worm Eisenia andrei is reported. Uptake of As, Cd, Cr, Cu, Ni, Pb, and Zn in 20 Dutch field soils and in OECD artificial soil was quantified as a function of time. Internal metal concentrations varied less than the corresponding external levels. Metal uptake and elimination were both metal- and species-dependent. Worms typically attained steady-state concentrations rapidly for Cr, Cu, Ni, and Zn. Internal concentrations similar to those in the cultivation medium, linearly increasing body concentrations, or steady-state internal concentrations well above those in the cultivation medium were found for As, Cd, and Pb. Multivariate expressions were derived to describe uptake rate constants, steady-state concentrations, and bioaccumulation factors as a function of soil characteristics. Soil acidity is the most important solid-phase characteristic modulating the availability of As, Cd, and Pb. Although additional semimechanistic calculations yielded evidence of pore-water-related uptake of Cd and Pb modulated by competition between H(+) and metal ions at the active sites of the membranes, the findings for Cr, Cu, Ni, and Zn point to additional influences, among which is probably regulation.     

Metal distribution in the earthworm,Pheretima hilgendorfi,and their variations with growth

The concentrations and distribution of metals (Fe, Mn, Zn, Cu, Pb, Ni, Co, As, Hg, and Cd) in an earthworm,Pheretima hilgendorfi, and their variations with growth were investigated. Higher concentrations of the metals were found in the pre-clitellar regions of the earthworm compared with the post-clitellar ones; Cd, Cu, and Hg were relatively high in the gut wall. The body concentration of Pb and Hg decreased with increased body length (age) and weight, while the opposite was found for Cd and As. The accumulation of Fe, Mn, Zn, Cu, Ni, and Co in the earthworm depends primarily on the metabolic turnover, whereas the accumulation of Pb, Hg, Cd and As, is dependent upon the age or exposure time. Small earthworms showed faster uptake and excretion rates of Pb and Hg than the large ones, and the biological half-lives of Pb and Hg were relatively short compared with those of Cd and As. The large earthworms exhibited a decrease of Hg in the bodies, probably due to excretion of Hgvia spawning. Based upon these results, the sizes and parts of the earthworm suitable for purposes of research are discussed.     

Influence of copper and iron on subacute cadmium intoxication in protein-malnourished rats

Male albino rats maintained on low-protein (9%) diets were dosed intraperitoneally with 0.75 mg Cd/kg, as cadmium chloride, for 20 days. Groups of these animals were provided with diets supplemented with 40 ppm Cu, 400 ppm Fe or a combination of both during the exposure period. Hepatic and renal distribution of Cd, Zn, Cu, and Fe along with activity of acid and alkaline phosphatases and ribonuclease and glutathione content were studied. Uptake of Cd both in liver and in kidney was significant and was accompanied by increased Zn and depletion of Fe concentration. The Cu level remained unaltered. Dietary supplementation of Cu or Fe interacted effectively and influenced the metal distribution. Acid and alkaline phosphatases in both liver and kidney were inhibited by Cd exposure. However, Cu and/or Fe supplements could to a varying degree offset the Cd-induced inhibition. Cadmium exposure did not, however, elicit any effect on hepatic and renal ribonuclease activity of low-protein-fed animals. The glutathione concentration registered profound increase on Cd exposure, possibly to act as a defence mechanism.     

Genotoxicity of heavy metals to the larvae of Chironomus kiiensis Tokunaga after short-term exposure

The genotoxic effects of increasing concentrations (below lethal concentration [LC??]) of cadmium ([Cd] 0.1, 1 and 10 mg/L), copper ([Cu] 0.2, 2 and 20 mg/L) and zinc ([Zn] 0.5, 5 and 50 mg/L) on Chironomus kiiensis were evaluated using alkaline comet assay after exposure for 24 h. Both the tail moment and the olive tail moment showed significant differences between the control and different concentrations of Cd, Cu and Zn (Kruskal-Wallis, p < 0.05). The highest concentration of Cd was associated with higher DNA damage to C. kiiensis larvae compared with Cu and Zn. The potential genotoxicity of these metals to C. kiiensis was Cd > Cu > Zn.     

Relationship of lead and cadmium to essential elements in hair, teeth, and nails of environmentally exposed people

The aim of this investigation was to evaluate the environmental exposure to Pb and Cd during 1990-1997 of inhabitants of Katowice District, which is an area of high environmental exposure to lead and cadmium, as well as exposure to Fe, Zn, Cu, Mn, Ni, Cr, Ca, Na, and K, on the basis of concentrations in hair, teeth, and nails. This investigation was to explain if accumulation of Pb and Cd can affect the concentration of such essential metals as Fe, Zn, Cu, and Ca. Inhabitants of the Beskid area constituted a control group. Analysis of the aforementioned elements was carried out on 624 hair samples, 785-tooth- samples, and 338 nail samples taking into consideration sex, age (<15, 16-30, >30 years), and type of teeth (incisor, canine, molar, premolar). Concentrations of elements in the media investigated were determined using atomic absorption spectroscopy. The results were calculated using the Statistica program. The major statistical analysis focuses on determining analysis of variance by MANOVA/ANOVA, Rao R (P<0.05), Spjotvolla-Stoline'a test, and cluster analysis (1-Pearson r). The investigation revealed that among the media investigated, Pb concentration in hair is an environmental marker of exposure to this metal in the human organism and depends on sex and age. It was also observed that an increase in Pb concentration in hair causes a decrease in Fe and Ca concentrations and changes the ratios of essential metals: Fe/Cu, Fe/Zn, and Ca/Zn. It is concluded that not only in blood but also in the hair, lead significantly influences Ca and Fe. Analysis of nail samples of people living in Katowice District indicated that an increasing concentration of Pb decreases concentrations of copper and zinc. Increased accumulation of such metals as Ni, Cr, and Mn in teeth was observed for samples taken from inhabitants of Katowice District.     

Biokinetics of cadmium and zinc in a marine bacterium: influences of metal interaction and pre-exposure

The uptake kinetics of Cd and Zn, as influenced by metal interaction and metal pre-exposure, was examined in the gram-positive marine bacterium Bacillus firmus over a wide range of ambient free-Cd and -Zn concentrations. Bacteria were exposed to experimental media with different concentrations of Cd and Zn over a short, 15-min period. Zinc was found to be an effective competitive inhibitor of Cd uptake when the Zn(2+) concentration ([Zn(2+)]) was increased to 10(-8) M, whereas the Cd concentration (ranging from 10(-9) to 10(-6) M) did not affect Zn uptake. Inhibition of Cd uptake was dependent on [Zn(2+)] instead of the [Zn(2+)] to Cd(2+) concentration ratio. Cadmium uptake at different [Zn(2+)] was significantly inhibited by a sulfur ligand (SH) blocker (N-ethylmaleimide) and a Ca-channel blocker (lanthanum), suggesting that competition between Cd and Zn most likely occurred via binding to the same transport sites. Cadmium efflux also was determined in the presence of different [Zn(2+)]. A biphasic depuration of Cd was found when [Zn(2+)] was greater than 10(-8) M, whereas the calculated Cd efflux rate was independent of [Zn(2+)]. We further exposed B. firmus at different Cd or Zn concentrations for 24 h, then determined the metal uptake and efflux kinetics as well as the metallothionein (MT) induction. Both the Cd and Zn cellular concentrations increased with greater exposed metal concentration, but the MT levels and efflux were little affected by the elevated metal concentration. To some extent, however, the Cd uptake was reduced with an elevated intracellular Zn concentration, suggesting that at high Cd concentrations, intracellular Zn can suppress the Cd uptake in B. firmus. These results help to understand the interactions of metals in the marine environments.     

The effect of low doses of dietary cadmium oxide on the disposition of trace elements (zinc,copper, iron), hematological parameters,and liver function in rats

The Zn, Cu, and Fe concentrations in selected organs, tissues and in the excreta of male Wistar rats, exposed to dietary CdO (2.80 and 7.15 ppm) for 40 and 60 days, were investigated. Concomitantly hematological values and serum enzyme activities were recorded. Zn levels of spleen, kidney, testes, muscle and feces were not affected by the Cd treatment. After 40 days of Cd exposure, the Zn concentration in the hair decreased, while the Zn level of the lung slightly increased. During the feeding trial, Cd produced an increase of liver Zn by about 24%. Femur Zn decreased and Zn in urine increased after 60 days of exposure to 7.15 ppm Cd. Except in hair and urine, the Cu concentration in all organs and tissues investigated remained unchanged. Hair Cu levels decreased after 40 days of Cd exposure but increased after 60 days. At this time, elevated Cu concentration in urine was recorded. After exposure to 7.15 ppm Cd, the Fe content of the lung, liver, spleen, testes, muscle, femur and blood decreased significantly. After 60 days on the 7.15 ppm diet, highest reductions (30%–60%) of Fe content were recorded in the lung, liver, and spleen. Similar to Zn and Cu, the Fe concentration in urine increased at that time. No changes were found in the Fe content of hair, kidney, and feces. In spite of a disturbed Fe metabolism, an anaemic response of Cd-treated rats was not observed. Hematocrit and hemoglobin remained unchanged and the number of red blood cells slightly increased after 40 days of Cd exposure. While the activity of serum alkaline phosphatase was not affected by dietary Cd, the activities of serum-GOT and serum-GPT increased after exposure to 7.15 ppm Cd indicating disturbed hepatic functions.     

Potential Toxic Metal Accumulation in Soil,Forage and Blood Plasma of Buffaloes Sampled from Jhang,Pakistan

This study was conducted to determine the concentration of toxic metals in soil, forage and blood plasma of lactating and non-lactating buffaloes in the district Jhang, Punjab, Pakistan. Soil samples were collected from varying distances from the road side. Plasma separation was achieved by centrifugation. The concentration of arsenic (As), selenium (Se), cadmium (Cd), chromium (Cr), iron (Fe), zinc (Zn), copper (Cu) and cobalt (Co) were determined by using Atomic Absorption Spectrophotometer. The results of the study showed that the mean As, Se and Cd concentrations in soil samples were lower while Cr, Fe, Zn, Cu and Co were higher than the official guidelines. In plasma samples, mean concentration values of Co, Zn, Fe, Cd, Se and As were lower while Cu and Cr were higher than the recommended concentrations. According to the results of the study there was no potential exposure of toxicity in buffaloes of the study area.     

Toxicity of metal mixtures to a tropical freshwater alga (Chlorella sp): the effect of interactions between copper,cadmium, and zinc on metal cell binding and uptake

The individual and combined effects of copper, cadmium, and zinc on the cell division rate of the tropical freshwater alga Chlorella sp. were determined over 48 to 72 h. Metal mixtures were prepared based on multiples of their single-metal median effective concentration (EC50) values, i.e., toxic units (TU) using a triangular mixture design with five toxicant levels (0, 0.75, 1.0, 1.25, and 1.5 TU). Single-metal EC50 values after a 72-h exposure were 0.11, 0.85, and 1.4 microM for copper, cadmium, and zinc, respectively. Significant interactions were observed for all metal combinations after 48 and 72 h. An equitoxic mixture of Cu + Cd was more than concentration additive (synergistic) to the growth of Chlorella sp., while combinations of Cu + Zn, Cd + Zn, and Cu + Cd + Zn were all less than concentration additive or were antagonistic. To determine the effect of each metal on the uptake of the other, extracellular (membrane-bound) and intracellular metal concentrations, both alone and in mixtures, were compared. The increased growth inhibition observed for mixtures of Cu + Cd was due to higher concentrations of cell-bound and intracellular copper in the presence of cadmium compared with copper alone (i.e., cadmium-enhanced copper uptake). In contrast, both extra- and intracellular cadmium concentrations were reduced in the presence of copper. In mixtures of Cu + Zn, copper also inhibited the binding and cellular uptake of zinc, which resulted in decreased toxicity. Zinc had no appreciable effect on the uptake of copper by Chlorella sp. Our results suggest that all three metals share some common uptake and transport sites on Chlorella cells and that copper out competes both cadmium and zinc for cell binding. Determination of metal cell distribution coefficients (K(d)) confirmed that K(d) values for cadmium and zinc in single-metal exposures decreased in the presence of copper.     

Cadmium Interaction with Essential Metals (Zn, Cu, Fe), Metabolism Metallothionein, and Ceruloplasmin in Pregnant Rats and Fetuses

Cadmium administered to rats per os is accumulated in the duodenal mucosa in the form of metallothionein (MT). Therefore, this toxic metal can influence the efficiency of essential metal absorption, especially their concentration in the maternal organism, which plays an essential role during fetal development. The aim of this study is to elucidate the mechanism of the origin of Zn, Cu, and Fe deficiency in fetal rat livers after maternal exposure to cadmium in drinking water and to investigate the roles of MT and ceruloplasmin (Cp) in this phenomenon. Cadmium was given to pregnant dams exposed for 0–20 days of gestation in drinking water at concentrations of 6.25–100 μg Cd/ml. After cessation of exposure, at the lowest dose, a decrease in Cu and Fe concentrations in the duodenal mucosa was found. Simultaneously, diminution in concentration of two cited metals and Cp activity in serum of dam blood was noted. The lowest dose of cadmium developed a drop tendency in microsomal fetal liver iron. Significant correlations were observed between fetal liver Cu contents and Cp activity in serum of dams and Cu concentrations in serum of dams. Diminished Cp activity in serum of dams is related to reduced availability of Cu and Fe in fetuses. In conclusion, it is suggested that the mechanism of Cu and Fe deficit content in fetuses is based on the diminution of absorption of these metals by dam intestines exposed to cadmium on the reduction of metal concentrations in blood serum and, in consequence, their decreasing availability in fetuses.