Toxicity and mutual interactions of cadmium and zinc ions in normal and carcinogen-transformed mouse cells

The toxicity of chloride salts of physiological (zinc, manganese, nickel) and non physiological (cadmium) bivalent metal ions was studied in normal or carcinogen-transformed mouse embryo fibroblast cells. The dose response curves for toxicity to both types of cells exhibited similar shapes. The transformed cells, however, were about twice as sensitive to zinc toxicity as normal cells. When normal and transformed cells were grown together and incubated for several hours with an appropriate concentration of zinc, the malignant cells were selectively killed. Cadmium was much more toxic than the three other metal ions in both types of cells. Its toxic effect was reversed by simultaneous addition of zinc at nontoxic concentrations.Abbrevications CFA colony forming ability - MCA 3-methylcholanthrene     

Interaction of mineral elements in sea water and shell of oysters (Crassostrea virginica (Gmelin)) cultured in controlled and natural systems

The interaction is reported of selected chemical elements (cadmium, calcium, copper, iron, magnesium, manganese, strontium, and zinc) in cultured sea water, with soft tissues, prismatic calcite of the right valve, and foliated calcite of right and left valves of genetically similar American oysters, Crassostrea virginica (Gmelin) grown in a natural habitat and in two environmentally controlled experimental systems (flow-through and recycle). The addition of trace elements as algal nutrients in ambient sea water was reflected in higher concentrations of trace metals in shells and soft tissues of oysters grown in experimental systems. Calcium was relatively uniformly distributed in major regions of valves from the three habitats, even though its concentration fluctuated widely in sea water in experimental systems. Magnesium and strontium were most concentrated in valves of oysters grown in the recycle system (magnesium in the prismatic layer of the shell and strontium in the foliated calcite). Iron was uniformly distributed. Cadmium, copper, manganese, and zinc were most concentrated in the prismatic calcite of valves from the flow-through system. In soft tissues, calcium was more concentrated in oysters from experimental systems than in those from the natural habitat. Manganese was about equally distributed in soft tissues from the three habitats, whereas copper and iron were more concentrated in soft tissues in experimental systems than in the natural habitat, and were many times more concentrated in soft tissues than in valves from all three habitats. As concentrations of magnesium, strontium, mangenese, zinc, and cadmium increased in valves in experimental systems, pigmentation of valves decreased. The study confirmed the capacity of oysters to concentrate several elements in their valves as concentration of these elements increased in ambient sea water and disclosed the heterogeneous distribution of these elements in major regions of the valves.     

Isolation and Identification of a New Analogue of Aspergillic Acid Derived from Valine and Isoleucine

The biological activities of zinc and cadmium on Euglena gracilis grown in zinc deficient and sufficient media were examined- Cadmium was neither involved in the normal cell metabolism of E. gracilis under zinc deficient conditions, nor did not replace zinc, which is essential for the normal growth. More cadmium was incorporated into cells grown in zinc deficient media than in zinc sufficient ones, resulting in more toxic effects in zinc deficient media than in zinc sufficient ones. Cadmium effectively provoked abnormal cells under zinc deficient conditions, suggesting that the normal process of cell division was interrupted by cadmium.     

Effect of dietary calcium on cadmium absorption and retention in suckling rats

The effect of calcium supplementation on absorption and retention of cadmium in the suckling period was evaluated in Wistar rat pups of both sexes. Animals were maintained in the litters with the mother rats and supplemented with 1%, 3% or 6% calcium (as CaHPO₄×2H₂O) in cow's milk by artificial feeding from day of birth 6 through 14. All rats were exposed to cadmium (as CdCl₂×H₂O) either orally or parenterally. Oral cadmium dose of 0.5 mg/kg body weight a day was administered through nine-day period of calcium supplementation and parenteral cadmium dose was injected subcutaneously in a single dose of 0.5 mg Cd/kg body weight prior to calcium supplementation. On experimental day 10 (at the age of pups of 15 days) all animals were killed and the liver, kidneys, brain and carcass (body without organs and skin) were removed for element analyses. Cadmium and essential elements calcium, zinc and iron were analysed in the tissues by atomic absorption spectrometry. Results showed that after oral exposure cadmium concentrations in all calcium-supplemented groups were significantly decreased in the organs and carcass and that the effect was dose-related. No such effect of calcium was found after parenteral cadmium exposure. Calcium supplementation per se significantly increased calcium concentration in the carcass and had no effect on iron in organs and zinc in carcass. It was concluded that calcium supplementation during the suckling period could be an efficient way of reducing oral cadmium absorption and retention without affecting tissue essential trace element concentrations.     

Studies on cadmium localization in the water fern Azolla

Uptake of cadmium by the water fern Azolla filiculoides (Lamarck) was characterized, and the localization of the metal in the roots and shoots as well as its effects on some essential elements were studied. Cadmium was accumulated at a rapid rate in Azolla plants within 1 h and then more gradually up to 77 h. Cadmium content was increased in the inner epidermis, cortex and bundle cell walls of the root between 33 and 77 h. This accumulation was characterized by the appearance of small dark grains with high content of cadmium, phosphate and calcium along the epidermal cells. The shoots of Azolla plants grown in the presence of cadmium showed high content of cadmium only in the ventral lobe submerged in the growth medium, suggesting that cadmium was absorbed directly from the medium. The effect of cadmium on essential elements in Azolla was characterized by simultaneous increases in calcium and cadmium content in the root and shoot and by decreases in magnesium content in the root and potassium content in the shoot.     

Effects of Nano-zinc on Biochemical Parameters in Cadmium-Exposed Rats

Cadmium (Cd) is a toxic environmental and occupational pollutant with reported toxic effects on the kidneys, liver, lungs, bones, and the immunity system. Based on its physicochemical similarity to cadmium, zinc (Zn) shows protective effects against cadmium toxicity and cadmium accumulation in the body. Nano-zinc and nano-zinc oxide (ZnO), recently used in foods and pharmaceutical products, can release a great amount of Zn²⁺ in their environment. This research was carried out to investigate the more potent properties of the metal zinc among sub-acute cadmium intoxicated rats. Seventy-five male Wistar rats were caged in 15 groups. Cadmium chloride (CdCl₂) was used in drinking water to induce cadmium toxicity. Different sizes (15, 20, and 30 nm) and doses of nano-zinc particles (3, 10, 100 mg/kg body weight [bw]) were administered solely and simultaneously with CdCl₂ (2–5 mg/kg bw) for 28 days. The experimental animals were decapitated, and the biochemical biomarkers (enzymatic and non-enzymatic) were determined in their serum after oral exposure to nano-zinc and cadmium. Statistical analysis was carried out with a one-way ANOVA and t test. P < 0.05 was considered as statistically significant. The haematocrit (HCT) significantly increased and blood coagulation time significantly reduced in the nano-zinc-treated rats. AST, ALT, triglyceride, total cholesterol, LDL, and free fatty acids increased significantly in the cadmium- and nano-zinc-treated rats compared with the controls. However, albumin, total protein, and HDLc significantly decreased in the cadmium- and nano-zinc-treated rats compared with the controls (P < 0.05). It seems that in the oral administration of nano-zinc, the smaller sizes with low doses and the larger sizes with high doses are more toxic than metallic zinc. In a few cases, an inverse dose-dependent relationship was seen as well. This research showed that in spite of larger sizes of zinc, smaller sizes of nano-zinc particles are not suitable for protection against cadmium intoxication.     

Cadmium uptake and toxicity via voltage-sensitive calcium channels

The mechanism of cellular uptake of cadmium, a highly toxic metal ion, is not known. We have studied cadmium uptake and toxicity in an established secretory cell line, GH4C1, which has well characterized calcium channels. Nimodipine, an antagonist of voltage-sensitive calcium channels, protected cells against cadmium toxicity by increasing the LD50 for CdCl2 from 15 to 45 microM, whereas the calcium channel agonist BAY K8644 decreased the LD50. Organic calcium channel blockers of three classes protected cells from cadmium toxicity at concentrations previously shown to block high K+-induced 45Ca2+ influx and secretion. Half-maximal protective effects were obtained at 20 nM nifedipine, 4 microM verapamil, and 7 microM diltiazem. Increasing the extracellular calcium concentration from 20 microM to 10 mM also protected cells from cadmium by causing a 5-fold increase in the LD50 for CdCl2. Neither the calcium channel antagonist nimodipine nor the agonist BAY K8644 altered intracellular metallothionein concentrations, while cadmium caused a 9-20-fold increase in metallothionein over 18 h. Cadmium was a potent blocker of depolarization-stimulated 45Ca2+ uptake (IC50 = 4 microM), and the net uptake of cadmium measured with 109Cd2+ was less than 0.3% that of calcium. Although the rate of cadmium uptake was low relative to that of calcium, entry via voltage-sensitive calcium channels appeared to account for a significant portion of cadmium uptake; 109Cd2+ uptake at 30 min was increased 57% by high K+/BAY K8644, which facilitates entry through channels. Furthermore, calcium channel blockade with 100 nM nimodipine decreased total cell 109Cd2+ accumulation after 24 h by 63%. These data indicate that flux of cadmium through dihydropyridine-sensitive, voltage-sensitive calcium channels is a major mechanism for cadmium uptake by GH4C1 cells, and that pharmacologic blockade of calcium channels can afford dramatic protection against cadmium toxicity.     

Effects of Cadmium on Aquatic Hyphomycetes

Two kinds of experiments, sporulation and growth experiments, were carried out to demonstrate the effect of cadmium on aquatic hyphomycetes. Oak (Quercus petraea L.) leaves were exposed in a hard-water stream (Lüssel, Swiss Jura) and a soft-water stream (Ibach, Black Forest) for 2 months. In the laboratory, fungal sporulation on the leaves in stream water enriched with cadmium (as CdCl₂) was studied. A measurable effect was found when the cadmium concentration exceeded 0.1 ppm (0.1 mg/liter). Concentrations higher than 100 ppm inhibited conidium production completely. This toxic effect of cadmium was species dependent and much higher in soft water (water with low concentrations of calcium and magnesium) than in hard water. Growth experiments with Alatospora acuminata Ingold, Clavariopsis aquatica De Wildeman, Flagellospora curvula Ingold, Heliscus lugdunensis Saccardo and Therry, and Tetracladium marchalianum De Wildeman showed the same pattern of cadmium sensitivity as that seen in the sporulation experiments. Mycelial growth was less sensitive to cadmium than was fungal sporulation. High concentrations of competing cations (e.g., calcium and zinc) or potential ligands could reduce cadmium toxicity. Calcium content seems to be the most important factor responsible for the different sensitivity of aquatic hyphomycetes in hard and soft water.     

Effects of Metals on Streptomyces coelicolor Growth and Actinorhodin Production

Actinorhodin production by Streptomyces coelicolor was used as a model system to study the effects of metals on growth and polyketide synthesis in a streptomycete. Numerous metals were tested in cultures grown in liquid media. Mercury and cadmium were highly toxic, and copper, nickel, and lead were less so, but all tended to inhibit both growth and antibiotic synthesis to a similar extent. Unexpectedly, manganese, cobalt, zinc, and, to a lesser extent, chromium caused complex effects that in general resulted in some enhancement of growth yield but a reduction in antibiotic titers. These complex effects meant that cobalt, manganese, and zinc had lower 50% inhibitory concentrations for antibiotic yields compared with those for biomass. The physiologically active divalent cations calcium and magnesium were also tested. Calcium at high concentrations was particularly effective in reducing antibiotic titers and enhancing growth yields. By adding calcium at different phases of growth, it could be demonstrated that it was most effective in reducing the antibiotic yield when added during the early growth phase. Addition during the antibiotic-producing phase resulted in little reduction of final actinorhodin titers.     

Cadmium toxicity in animal cells by interference with essential metals

Cadmium is found in the environment as part of several, mainly zinc-rich, ores. It has been used in many technological applications, but biological systems generally failed to safely deal with this element. In mammalian biology, cadmium exposure jeopardizes health and mechanisms of cadmium toxicity are multifarious. Mainly because bioavailable cadmium mimics other metals that are essential to diverse biological functions, cadmium follows a Trojan horse strategy to get assimilated. Metals susceptible to cadmium deceit include calcium, zinc, and iron. The wealth of data addressing cadmium toxicity in animal cells is briefly reviewed with special emphasis on disturbance of the homeostasis of calcium, zinc, and iron. A limited number of tissues and cell types are considered as main targets for cadmium toxicity. Still, the diversity of pathways affected by cadmium exposure points to a more general threat to basic cellular functions. The poor efficiency of cellular export systems for cadmium explains the long residence time of the element in mammals. Therefore, proper disposal and educated uses of this technologically appealing, but biologically malicious, element should be favored in the future. The comprehensive knowledge of cadmium biological effects is indeed a necessary step to protect human and animal populations from environmental and anthropological exposures.     

Effects of essential divalent metals on carcinogenicity and metabolism of nickel and cadmium

Interactions between the physiologically essential metals calcium, magnesium, and zinc and the carcinogenic metals nickel and cadmium were investigated to help elucidate the mechanisms of action of the carcinogenic metals. Bioassay studies revealed several significant findings, including: (1) the ability of magnesium and calcium to inhibit nickel-induced elevation of pulmonary adenoma incidence in strain A mice; (2) the ability of magnesium, but not of calcium, to prevent cadmium-induced subcutaneous sarcoma formation; and (3) the ability of magnesium, but not of calcium, to inhibit nickel-induced muscle tumor formation. Biochemical studies indicated a direct relationship between the antitumorigenic potential of magnesium and the capacity of this metal to: (1) inhibit nickel and cadmium uptake by the target tissues in vivo; (2) inhibit nickel-induced disturbances in DNA synthesis in vivo; (3) inhibit nuclear and cytosolic uptake of nickel by the target tissue cells in vivo; and (4) inhibit nickel and cadmium binding to DNA in vitro. Calcium, which in most cases did not prevent carcinogenesis, had no consistent influence on the uptake of carcinogenic metals or their biochemical effects in the target tissues. Magnesium and zinc, but not calcium, were also found to attenuate the acute toxic effects of nickel, indicating a possible correlation between prevention of acute effects and reduction in tumorigenicity. Zinc, which antagonizes cadmium tumorigenicity in the rat testis, was found to reduce markedly cadmium uptake into isolated testicular interstitial cells. Also, zinc was found to inhibit strongly cadmium binding to DNA in vitro.     

Cation binding properties of calretinin, an EF-hand calcium-binding protein.

Calretinin (CR) is a neuronal EF-hand protein previously characterized as a calcium (micromolar affinity) binding protein. CR-containing neurons are spared in some neurodegenerative diseases, although it is as yet unconfirmed how CR plays an active role in this protection. Higher levels of some metal cations (e.g. copper and zinc) are associated with these diseases. At the same time, metals such as terbium (NMR and fluorescence) cadmium (NMR) and manganese (EPR) serve as useful calcium analogues in the study of EF-hand proteins. We survey the binding of the above-mentioned metal cations that might affect the structure and function of CR. Competitive 45Ca2+-overlay, competitive terbium fluorescence and intrinsic tryptophan fluorescence are used to detect the binding of metal cations to CR. Terbium and copper (half-maximal effect of 15 microM) bind to CR. Terbium has a similar or greater affinity for the calcium-binding sites of CR than calcium. Copper quenches the fluorescence of terbium-bound CR, and CR tryptophan residues and competes weakly for 45Ca2+-binding sites. Cadmium, magnesium, manganese and zinc bind less strongly (half-maximal effects above 0.1 mM). Therefore, only terbium appears to be a suitable analytical calcium analogue in further studies of CR. The principal conclusion of this work is that copper, in addition to calcium, might be a factor in the function of CR and a link between CR and neurodegenerative diseases.     

Lead and cadmium toxicity in established mammalian cell lines]

Lead and cadmium toxicity was evaluated in three mammalian cell lines (tumour : HeLa, transformed : XC and normal : NRK) by means of the modifications of the 3H-TdR incorporation rate in the nucleus of the treated cells. The three cell lines showed different degrees of sensitivity. Sensitivity depended on the line, metal, its concentration and duration of incubation. Cadmium was found to be at least five times more toxic than lead except at low concentration. The normal cell line was more sensitive to cadmium and less sensitive to lead than other lines.     

Localization and toxic effects of cadmium, copper, and uranium in azolla

The storage and distribution of copper, cadmium, and uranium and their effects on ionic contents in roots and shoots of Azolla filiculoides has been studied by x-ray microanalysis. The relative content of copper was eightfold higher in the root than in the shoot, suggesting low mobility of this metal in Azolla plant. Cadmium relative content in the shoot was similar to its content in the root, hence its mobility was relatively high. The absence of significant uranium quantities in the shoot and its relative high content in the root suggest the immobility of this metal from Azolla root. Cadmium formed precipitates with phosphate and calcium in xylem cells of the shoot bundle and caused a two- to threefold increase in the content of phosphate in the root. Uranium in roots and cadmium in shoots were associated with calcium. All three treatments caused losses of potassium, chloride, and magnesium from Azolla roots. Accumulation of heavy metals in Azolla and their mobility from the root to the shoot can be correlated with damage caused by the loss of essential nutrients.     

Effects of acute exposure to cadmium (II) chloride and lead (II) chloride on the haematological profile of Oreochromis aureus (Steindachner)

1. Oreochromis aureus (Steindachner) was exposed to two concentrations of lead and cadmium for 24 hr and 1 week to assess the effects of these pollutants on haematological parameters.2. Plasma osmolality was found to be the most sensitive blood parameter, affected before other parameters changed.3. Cadmium appears to be more toxic to O. aureus than lead, having an adverse effect on blood parameters earlier than lead.4. In the earlier stages of toxicity cadmium appears to have a more pronounced effect on haemoglobin concentration than lead.5. Cadmium does not depress erythrocyte counts but lead does.     

Effects of cadmium and zinc ions on purified lamb kidney cortex glucose-6-phosphate dehydrogenase activity

Glucose-6-phosphate dehydrogenase (G-6-PD) is the first enzyme in the pentose phosphate pathway. Cadmium is a toxic heavy metal that inhibits several enzymes. Zinc is an essential metal but overdoses of zinc have toxic effects on enzyme activities. In this study G-6-PD from lamb kidney cortex was competitively inhibited by zinc both with respect to glucose-6-phosphate (G-6-P) and NADP+ with Ki values of 1.066 +/- 0.106 and 0.111 +/- 0.007 mM respectively whereas cadmium was a non-competitive inhibitor with respect to both G-6-P and NADP+ Ki values of 2.028 +/- 0.175 and 2.044 +/- 0.289 mM respectively.     

Combination ecotoxicity and testing of common chemical discharges to sewer using the<Emphasis Type="Italic"> Vibrio fischeri</Emphasis> luminescence bioassay

In order to investigate possible synergistic or antagonistic (more or less than additive) toxicity effects, mixtures of chemicals were tested in water using a microbial bioassay. Ten toxicants (3,4-dichloroaniline, 3,5-dichlorophenol, cadmium, chromium, copper, Lindane, linear alkylbenzene sulphonate, pentachlorophenol, toluene, zinc) were chosen on the basis of their common occurrence in industrial effluents within local waste water treatment plants. These toxicants also cover a wide range of modes of toxic action, namely, polar and non-polar narcosis, membrane disruption, respiratory disruption, uncouplers of oxidative phosphorylation, biochemical disruption and enzyme inhibition. Efficient screening for possible combination toxicity between toxicants involved testing the chemicals both singly and in triplet combinations. The triplets were based on four replicates of a balanced incomplete block design (BIB). A standardised Vibrio fischeri rapid toxicity bioluminescence assay was used. The combinations tested showed that only one mixture was found to be significantly more toxic than expected from the pure single-toxicant results. Two triplets were significantly less toxic. Further tests on the more toxic triplet showed that the effect was due to only one of the 45 pairs originally screened. It is concluded that synergistic effects in combinations of toxicants are rather rare in bioluminescence systems utilising common effluents discharged to sewer. Electronic Publication     

Influence of Cadmium, Zinc, and Lead on Growth, Trap Formation, and Collagenase Activity of Nematode-Trapping Fungi

Growth and morphogenesis of seven species of nematode-trapping fungi and the activity of a collagenase produced by Arthrobotrys amerospora were measured in the presence of various concentrations of divalent cadmium, zinc, or lead. In general, growth varied with species and was dependent on the metal present and the concentration at which it was tested. Cadmium was found to exhibit the greatest toxicity followed by zinc and lead, respectively. In most cases, inhibition of growth was directly correlated with a decreased capacity to form traps. However, in a few cases, trap formation was inhibited either more or less than was growth. The activity of the collagenase was less sensitive than was growth or trap formation to heavy-metal inhibition.     

Effects of cobalt, magnesium, and cadmium on contraction of rat soleus muscle.

The effects on isometric tension of three divalent ions that block calcium channels, magnesium, cobalt, and cadmium, were tested in small bundles of rat soleus fibers. Cobalt, at a concentration of 2 or 6 mM, reversibly depressed twitch and tetanic tension and the depression was much greater in solutions containing no added calcium ions. Magnesium caused much less depression of tension than cobalt. The depression of tension was not accompanied by membrane depolarization or a reduction in the amplitude of action potentials. A reduction caused by 6 mM cobalt in the amplitude of 40 or 80 mM potassium contractures was not accompanied by a comparable reduction in tension during 200 mM potassium contractures, and could be explained by a shift in the potassium contracture tension-voltage curve to more positive potentials (by +7 mV on average). Similar effects were not seen with 2 or 6 mM magnesium. At a concentration of 20 mM, both cobalt and magnesium depressed twitch and tetanic tension, cobalt having greater effect than magnesium. Both ions shifted the potassium contracture tension-voltage curve to the right by +5 to +10 mV, caused a small depression of maximum tension, and slowed the time course of potassium contractures. Cadmium (3 mM) depressed twitch, tetanic, and potassium contracture tension by more than 6 mM cobalt, but experiments were complicated by the gradual appearance of large contractures that became even larger, and sometimes oscillatory, when the solution containing cadmium was washed out. It was concluded that divalent cations affect both activation and inactivation of tension in a manner that cannot be completely explained by a change in surface charge.