Comparative distributions of zinc, cadmium and mercury in the tissues of experimental mice

Different groups of mice were injected with cadmium, zinc and mercury. Zinc injections had no effect on zinc tissue levels while both mercury and cadmium accumulated in various tissues. Cadmium persisted in the tissues much longer than mercury, and while the mercury concentrations began to decline as soon as dosing ceased, cadmium concentrations in kidney and intestine increased even after dosing ceased. There appeared to be an interrelationship between cadmium concentrations in spleen and intestine which warrants some further investigations. There was a linear, but discontinuous, effect of cadmium on zinc concentrations in liver, kidney and pancreas which may depend on metallothionein biochemistry. Mercury injections had no effect on zinc metabolism. It is proposed that differences in the rate of excretion of cadmium and mercury from the kidney could explain the differential accumulation of cadmium and mercury in animals.     

Properties of metallothionein induced by zinc, copper and cadmium in the frog, Xenopus laevis

1. Repeated injections of zinc (Zn) and copper (Cu) into the frog Xenopus laevis caused accumulations of the respective metals in the liver and kidney. 2. The accumulated metals in the liver supernatant fractions were present as Zn- and Cu-binding proteins of the same properties as that of metallothionein (MT) induced by cadmium (Cd) injections. 3. The affinity of Zn, Cu and Cd ions to the metal-binding protein was in the decreasing order of Cu, Cd and Zn. 4. The Xenopus MT induced by Cd was unstable and disrupted easily to give two peaks as if the MT consists of two isometallothioneins.     

Metallothionein content in tissue and neoplasms of mice under cadmium chloride administration and gamma irradiation. Increased radioresistance in mice with elevated level of metallothionein

It was confirmed that the survival of gamma-exposed mice became higher after preliminarily subcutaneous injections of cadmium chloride. It is supposed that radioresistance of mice is connected with the induction of metallothionein proteins by cadmium chloride.     

Cadmium and lead toxicity effects on zinc, copper, nickel and iron distribution in the developing chick embryo

The teratologic effects on chicken embryos induced by the load of 100 micrograms of cadmium or lead nitrate salts injected into the yolk on day 5 of incubation as well as their effects upon zinc, copper, nickel and iron distribution were studied. Despite a significant teratologic influence of lead, cadmium administration did not induce significant effects. A week after injections, embryo lead content, but not cadmium concentration, increased; this differential action suggested an active uptake of lead by the embryo, not observed for cadmium. Both cadmium and lead affected significantly the iron, copper and zinc homeostasis in the egg. Cadmium induced these changes probably through alterations in the metallic ion transport processes towards the embryo.     

Induction of micronuclei and other nuclear abnormalities in European minnow Phoxinus phoxinus and mollie Poecilia latipinna: an assessment of the fish micronucleus test

In this work, we have measured both micronuclei and other nuclear abnormalities in renal erythrocytes from European minnow Phoxinus phoxinus and mollie Poecilia latipinna, with the aim to contribute to the standardisation of the micronucleus test for fish species. Intraperitoneal injections of colchicine (10 mg/kg), cyclophosphamide (40 mg/kg), or mitomycin C (20 mg/kg) for 24 h induced diverse nuclear abnormalities in minnow erythrocytes, therefore nuclear abnormalities should be added to micronuclei as genotoxicity indicators in fish micronucleus tests. The adequacy of administration protocols based on intraperitoneal injections has been evaluated by injecting saline solution to both species: single or double injections have not induced neither micronuclei nor other nuclear abnormalities in any case. Finally, the differential sensitivity of both species to toxic heavy metals was evaluated by exposing individuals of both species to different doses (0.17, 1.7, 2x1.7, and 3.4 mg/kg) of cadmium and mercury for 24 h; we concluded that the mollie is sensitive to both metals whereas the minnow is not sensitive to mercury.     

Interaction of benzo[a]pyrene, 2,3,3',4,4',5 hexachlorobiphenyl (PCB 156) and cadmium on biomarker responses in flounder (Platichthys flesus L.)

Interactive effects of a mixed pollutant exposure on biomarker responses were studied in European flounder (Platichthys flesus L.). The model chemicals, benzo[a]pyrene (BaP, 2.5 mg kg^-1), 2,3,3',4,4'5 hexachlorobiphenyl (PCB-156, 2.5 mg kg^-1), and cadmium (cadmium, 1 mg kg^-1), were administered to fish by subcutaneous injections. Biomarker responses were quantified both following administration of single chemicals and sequential combinations of the chemicals in pairs. Significant induction of CYP1A protein levels and corresponding ethoxyresorufin-O-deethylase (EROD) activities was observed in BaP and PCB treated flounder after 2 and 8 days, respectively. The strongest induction (44 fold) was caused by BaP. No further induction was observed after additional treatment with PCB 156. CYP1A induction caused by BaP was inhibited (40% compared with BaP treatment alone) in flounder pre treated with cadmium, whereas induction by PCB 156 appeared to be unaffected by pre treatment with cadmium. Flounder treated with cadmium only had significantly elevated hepatic levels of metallothionein (MT) after 15 days. Pre treatment with BaP and PCB prior to cadmium inhibited the MT induction (30-50%) compared with cadmium alone. Furthermore, significantly higher glutathione S transferase activities were observed in flounder administered cadmium alone, and in flounder treated with BaP or PCB 156 prior to cadmium. GST selenium independent peroxidase activities appeared to be unaffected by any of the treatments in the present study. The results indicate that chemical mixtures may affect biomarker responses differently from compounds administered alone, and that the sensitivity of both CYP1A and MT are influenced by pollutants other than their primary inducers.     

Induction of metal binding proteins in striped bass, Morone saxatilis, following cadmium treatment

1. The time course of induction of cytosolic metal binding proteins (MBP) was observed follow up to three daily intramuscular injections of cadmium chloride (0.2 mg cadmium/injection). 2. Low molecular weight binding proteins were resolved by gel permeation chromatography on Sephadex G-75. Based on total metal binding capacity, the concentration of crude MBP increased 2.6 fold. This level of induction of MBP was confirmed by polarographic analysis. 3. Initial binding of cadmium to MBP resulted in displacement of zinc, while at later times, zinc associated with MBP increased above control levels. 4. Using 35S-cysteine incorporation, it was shown that the rate of hepatic MBP synthesis was significantly greater than controls and sham injected fish 18 hr after the third cadmium injection. 5. Due to interfering proteins of molecular weights similar to the metal binding proteins one dimensional PAGE was not capable of verifying induction. However, the metal binding proteins were resolved using two dimensional gel electrophoresis.     

Interaction of benzo[a]pyrene, 2,3,3′,4,4′,5 hexachlorobiphenyl (PCB 156) and cadmium on biomarker responses in flounder (Platichthys flesus L.)

Interactive effects of a mixed pollutant exposure on biomarker responses were studied in European flounder (Platichthys flesus L.). The model chemicals, benzo[a]pyrene (BaP, 2.5 mg kg^-1), 2,3,3′,4,4′5 hexachlorobiphenyl (PCB-156, 2.5 mg kg^-1), and cadmium (cadmium, 1 mg kg^-1), were administered to fish by subcutaneous injections. Biomarker responses were quantified both following administration of single chemicals and sequential combinations of the chemicals in pairs. Significant induction of CYP1A protein levels and corresponding ethoxyresorufin-O-deethylase (EROD) activities was observed in BaP and PCB treated flounder after 2 and 8 days, respectively. The strongest induction (44 fold) was caused by BaP. No further induction was observed after additional treatment with PCB 156. CYP1A induction caused by BaP was inhibited (40% compared with BaP treatment alone) in flounder pre treated with cadmium, whereas induction by PCB 156 appeared to be unaffected by pre treatment with cadmium. Flounder treated with cadmium only had significantly elevated hepatic levels of metallothionein (MT) after 15 days. Pre treatment with BaP and PCB prior to cadmium inhibited the MT induction (30-50%) compared with cadmium alone. Furthermore, significantly higher glutathione S transferase activities were observed in flounder administered cadmium alone, and in flounder treated with BaP or PCB 156 prior to cadmium. GST selenium independent peroxidase activities appeared to be unaffected by any of the treatments in the present study. The results indicate that chemical mixtures may affect biomarker responses differently from compounds administered alone, and that the sensitivity of both CYP1A and MT are influenced by pollutants other than their primary inducers.     

Accumulation of cadmium in rat liver cadmium binding protein following single and repeated cadmium administration.

The accumulation of cadmium in rat liver cadmium binding protein induced by single and repeated intraperitoneal injections of CdCl2 and the de novo biosynthesis of CdBP were studied by using 109Cd to measure cadmium binding in the CdBP and 35S incorporation as indicator of protein synthesis. The biosynthesis of CdBP is controlled by the cadmium concentrations. For single doses up to 1 mg Cd2+/Kg b.w. about 50% of the cadmium is present in the soluble fraction of liver bound to CdBP and the incorporation of 35S-cysteine is linear with the cadmium concentration. When single doses ranging from 1 to 3 mg Cd2+/Kg b.w. are administered the fractions of both 35S-cysteine and cadmium incorporated into de novo synthesized CdBP gradually decrease. For single doses higher than 3 mg Cd2+/Kg b.w. the biosynthesis capability is maximum and 20 mug Cd/g liver can be incorporated into the de novo biosynthesized CdBP. When rats are treated every day with amounts of cadmium of about 0.8 mg Cd2+/Kg b.w. for up to 8 days a dose-proportional increase in both Cd incorporation and CdBP biosynthesis are observed. This shows a cumulative incorporation of cadmium in the de novo biosynthesized CdBP. Experiments carried out by injecting 65ZnCl2 and 203HgCl2 every day showed that they are not accumulated like cadmium and do not induce the biosynthesis of rat liver CdBP after repeated administration over 7 days.     

Isolation and characterization of a hepatic metallothionein from mice.

Mice were given cadmium chloride orally for 18 weeks, after which they were given two subcutaneous injections of cadmium chloride. Cadmium-and zinc-containing proteins were obtained from livers by ultracentrifugation, Sephadex chromatography and isoelectric focusing. Metallothionein with apI of 4.2 at 8 degrees C was separated from other proteins (possibly including other forms of metallothionein) by the isoelectric procedure. The metallothionein with pI = 4.2 had a high E250, reflecting abundant Cd-SH bonds, in accord with amino acid analysis, which gave a cysteine content of 34.6 residues % and showed an absence of aromatic amino acids. These results indicated a very high purity of the form of metallothionein isolated after isoelectric focusing.     

Induction of lipid peroxidation in hamster organs by the carcinogen cadmium: melioration by melatonin

Cadmium is a well-known human carcinogen. Lipid peroxidation is involved in cadmium-related toxicity and carcinogenesis. Melatonin is an effective antioxidant and free radical scavenger. The potential protective effects of melatonin against cadmium-induced lipid peroxidation in hamster brain, heart, kidney, testes, lung, and liver were examined. Lipid peroxidation was induced by intraperitoneal injection of cadmium chloride [single dose of 1 mg/kg body weight (bw)]. To test whether melatonin would protect against the toxicity of the carcinogen, the melatonin was injected peritoneally at a dose of either 15 mg/kg bw or 5 mg/kg bw, 0.5 h before cadmium treatment and thereafter at 8 h intervals during the day in the 48 h interval following the cadmium injection. One group of hamsters received only a single melatonin injection (a dose of 15 mg/kg bw, 30 min prior to cadmium). Forty-eight hours after cadmium injection, lipid peroxidation increased in brain, heart, kidney, testes, and lung. Either multiple injections of melatonin at both the 5 and 15 mg/kg bw doses, or a single injection of 15 mg/kg bw, prevented the cadmium-related increases in lipid peroxidation in brain, heart and lung. Cadmium-induced lipid peroxidation in kidney was prevented by melatonin when it was given as a single dose of 15 mg/kg bw. Melatonin slightly, but not significantly, reduced cadmium-induced lipid peroxidation in testes. It is concluded that cadmium toxicity, at least with regard to the resulting lipid peroxidation, is reduced by administering melatonin. This revised version was published online in July 2006 with corrections to the Cover Date.     

Rainbow trout metallothionein

Two forms of hepatic metallothionein were isolated and purified from rainbow trout injected intraperitoneally with cadmium chloride. Both forms showed similarities with mammalian metallothioneins, had a high cystein content (30 mol%), and were void of aromatic amino acids and histidine. The molecular weight was estimated to be about 6000 dalton for the apothioneins, and the thiol groups of the cysteine residues complexed with the heavy metals (Cd, Cu, Zn) in a SH/Me⁺⁺ ratio of about 2.4. The amount of copper in metallothionein from rainbow trout was very high, greater than the amount of cadmium and zinc after injections of 3 mg cadmium/kg body weight. The total metal content of cadmium, copper and zinc in metallothionein 1 and 2 were about 7 and 8 atoms per molecule respectively.     

Induction of micronuclei and sister chromatid exchange in bone-marrow cells and abnormalities in sperm of Algerian mice (Mus spretus) exposed to cadmium, lead and zinc

As a consequence of human activities, large amounts of cadmium, lead and zinc are released in the environment, often simultaneously. The aim of this study was to investigate under experimental conditions the DNA damage induced in Algerian mice (Mus spretus) exposed to cadmium (Cd), lead (Pb) and zinc (Zn) separately, or in selected combinations. Three cytogenetic end points were considered: the frequencies of micronucleated cells (MN) and sister chromatid exchange (SCE) in the bone marrow and the frequency of sperm abnormalities. Mice were treated by intraperitoneal (i.p.) injections with 5 or 10 doses of aqueous solutions of cadmium acetate, lead acetate and zinc acetate in concentrations corresponding to 1/10 of the LD50, respectively, 21.5, 0.46 and 1.5 mg/kg bw. The control groups were injected in the same way with distilled water.With only one exception (Cd + Zn group treated with 5 doses), the results show a significant increase of MN in all groups for both treatments (5 and 10 doses). Similarly, the results concerning the SCE revealed a statistically significant increase in all treated animals, with the exception of the Zn group treated with 5 doses. The number of sperm abnormalities was significantly higher in animals treated with 5 doses, except in the group Pb + Zn. In animals treated with 10 doses the number of sperm abnormalities was always statistically higher compared with controls.This study indicates that cadmium, lead and zinc can induce MN, SCEs and sperm abnormalities in Algerian mice and that the clastogenic potential is dependent on the time of exposure and the interaction between the three elements, confirming the environmental damage that may result from the simultaneous action of several metals. Most relevant is the toxic potential for Zn, related with the dose, which may compromise its protective effect against other metal contaminations, such as cadmium.     

Nephrotoxic action of platinum, chromium and cadmium compounds on marine bony fishes

Intra-abdominal injections of platinum, chromium and cadmium salts to Myoxocephalus scorpius produce nephrotoxic effect which includes the disturbances in magnesium secretion. Basic ultrastructural changes in the nephron cells of the fish after the injection of nephrotoxic substances are similar to those in mammals. Cis-platinum induces significant damage in the terminal part of the proximal tubules. One day after the injection of chromium compounds, total damage of the proximal tubule is observed, whereas cadmium salt affects cells within the whole nephron. After 5 days of administration of cadmium and chromium salts, partial recovery was found with respect to both functional and ultrastructural properties of nephron cells. Administration of nephrotoxic substances which selectively injure different parts of the nephron enabled to perform more exact differentiation of the nephron elements in marine teleosts.     

A comparison of the sequestration of cadmium and zinc in the tissues of rainbow trout (Salmo gairdneri) following exposure to the metals singly or in combination

Rainbow trout were exposed to either cadmium (9 micrograms/l) or zinc (100 micrograms/l) in their aquarium water. They were then transferred to water containing concentrations of cadmium (54 micrograms/l) that would have otherwise proved fatal to the majority of the fish without the pretreatment. Most of the fish survived under both sets of conditions. However, two different mechanisms seem to be involved in the protection of the animals against the toxic manifestations of cadmium. In both cases, more than 99% of the total body load of cadmium was found in the liver, kidney and gills of the animals. Analysis of the metal-binding proteins in these organs was carried out. In the fish exposed to the two concentrations of cadmium, the toxic metal was found only in association with two low mol. wt specific binding proteins despite the presence of zinc- (and copper)-containing isometallothioneins in all three organs. On the other hand, cadmium was distributed between these binding-proteins and metallothioneins in the liver, kidney and gill of the trout pretreated with zinc before their exposure to cadmium.     

Correlations between cadmium treatment, oxygen uptake and metallothionein response in liver and kidney from two mice strains

Oxygen uptake was determined in liver and kidney slices from Balb/C and C3H/HeJ mice at various time points related to a 4-day cadmium (Cd) i.p. injection regime, the latter strain being not only the higher metallothionein (MT) responder, but also more Cd sensitive. In both strains Cd injections caused an increase in O2 uptake in the tissues, being more expressed in the higher MT responsive C3H/HeJ strain. An ability for fast, additional increase of O2 uptake in response to subsequent Cd exposure was also induced during the injection regime. Maximal obtainable MT levels in the two strains were estimated by forced overwhelming pneumococcal infection challenge, giving induction values above those obtained for the Cd injections in the Balb/C strain and equal to those obtained for Cd in the more responsive C3H/HeJ strain. Together with direct defendants against harmful oxygen radicals, MT may act complementary as a radical scavenger and by Cd inactivation, but to a higher degree in the C3H/HeJ compared to the Balb/C strain.     

慢性镉负荷雄性大鼠的睾丸及生殖内分泌功能活动

选择健康SD雄性成年大鼠60只,随机分成对照组（C组）、镉负荷中剂量组（M组）和镉负荷高剂量组（H组）,每天分别饲喂含镉0,5,10mg/kg的大鼠全价饲料,连续6周,研究了镉负荷对大鼠睾丸及生殖内分泌功能活动的影响。结果显示：在整个实验期内,M和H组大鼠睾丸组织中的镉含量极明显上升,锌含量销有下降,与对照组差异不显著;血浆镉、锌含量虽分别表现稍有升高和下降,但与对照组比较无明显差异;H组睾丸精子头计数和每日精子生成量在镉负荷第3周极显著下降,第6周时,M和H组均极明显低于对照组;在整个实验期内,H组大鼠ALP活明显低于C组;LDH－X活性在M和H组大鼠均极明显低于C组;M和H组血浆T水平下降,均低于或显著低于C组;3组间的FSH和LH水平无明显差异。结果提示：慢性镉负荷在睾丸组织中逐步蓄积可引起睾丸一些酶活性改变、精子生成减少及内分泌功能活动低下。     

A comparison of the differential accumulation of cadmium in the tissues of three species of freshwater fish, Salmo gairdneri, Rutilus rutilus and Noemacheilus barbatulus

Roach and stone loach were exposed to cadmium dissolved in their aquarium water at 500 and 1250 micrograms/l, respectively, and the distribution of the metal accumulated in the major body organs was determined. The pattern of distribution for each species was somewhat different and was distinct in each case from that observed previously with rainbow trout. The total body loads of cadmium accumulated by the three species were assessed during the period of exposure and found not to correlate directly with the concentration of cadmium to which the individual species had been exposed. An alternative comparator was devised which as the quotient of the total body cadmium accumulation (microgram/100 g body wt) and the notional cadmium dose (microgram/l) X weeks was described as a fractional retention coefficient for cadmium. The coefficient was constant for each species at different periods of exposure to cadmium alone. The values of the coefficient for roach and stone loach were however much lower than that for rainbow trout. When rainbow trout were preexposed to zinc (100 micrograms/l, 5 days) before being exposed to cadmium, the fractional retention coefficient for cadmium fell to a value similar to those seen with roach and stone loach exposed to cadmium alone. The significance of these observations in relation to the nature of the intracellular proteins to which cadmium is bound in the three species is discussed in the light of their differential susceptibility to the toxic effects of cadmium.     

Fetal toxicity of cadmium chloride: the pharmacokinetics in the pregnant Wistar rat

The pharmacokinetics of a single subcutaneous injection of 40 mumol/kg CdCl2 in pregnant rats on day 18 were studied during an 18-hour time period. Previous studies demonstrated that this dose of CdCl2 induced fetal death, placental necrosis, and a reduction of uteroplacental blood flow without maternal lethality; direct fetal injections of CdCl2 indicated that the site of toxic action was not in the fetus. Cadmium was rapidly absorbed from the intrascapular subcutaneous depot with the highest blood levels occurring within 5 minutes of injection. The release from the depot appeared to be multiphasic with both rapid and slow absorption components observed in the blood. Uptake of cadmium was greatest in the liver, followed by the placenta, kidney, and pancreas. The best fit to the data was obtained by assuming the existence of two pools of cadmium in the organs: one freely exchangeable with the blood and the other nonexchangeable. Deviations from model predictions were observed for the placenta and adrenals; these deviations are consistent with the concomitant diminished blood flow to these organs. Cadmium uptake by the fetus was also investigated, and the results support the hypothesis that the placenta is relatively impermeable to the toxicant. It is concluded that the rapid and extensive accumulation of cadmium by the placenta may play a role in the development of early placental cellular damage and the eventual induction of fetal death through uteroplacental dysfunction.