Mammals cadmium

In mammals, cadmium inhibits copper absorption across the intestinal mucosa (Aaseth and Norseth 1986). Intercorrelations of copper with cadmium and zinc in livers of polar bears (Ursus maritimus) are probably mediated by metallothioneins, which may contain all three metals (Braune etal. 1991). In rats, copper protects against nephrotoxicity induced by cadmium, provided that copper is administered 24 h prior to cadmium insult. Specifically, rats given 12.5 mg Cu/kg BW by way of subcutaneous injection 24 h before receiving 0.4 mg Cd/kg BW — when compared to a group receiving Cd alone — did not have excessive calcium in urine and renal cortex or excessive protein in urine. Thus, 2.8 mg Cu/kg BW protects against 0.25 mg Cd/kg BW (Liu et al. 1992). 

In terrestrial mammals, cadmium tends to accumulate with increasing age in kidneys and livers of hares, moles and shrews, deer, caribou (Rangifer tarandus), and musk ox (Ovibos moschatus). Concentration of cadmium in kidney of deer increased from <0.002 mg/kg DW at age zero to 10.5 at age 7 years in males in females, these values were 6.5 mg/kg DW at age 3, 12.5 at age 7, and 20.0-... 

In mammals, as in yeast, several different metallothionein isoforms are known, each with a particular tissue distribution (Vasak and Hasler, 2000). Their synthesis is regulated at the level of transcription not only by copper (as well as the other divalent metal ions cadmium, mercury and zinc) but also by hormones, notably steroid hormones, that affect cellular differentiation. Intracellular copper accumulates in metallothionein in copper overload diseases, such as Wilson s disease, forming two distinct molecular forms one with 12 Cu(I) equivalents bound, in which all 20 thiolate ligands of the protein participate in metal binding the other with eight Cu(I)/ metallothionein a molecules, with between 12-14 cysteines involved in Cu(I) coordination (Pountney et ah, 1994). Although the role of specific metallothionein isoforms in zinc homeostasis and apoptosis is established, its primary function in copper metabolism remains enigmatic (Vasak and Hasler, 2000). 

Cooke, J. A. and M.S. Johnson. 1996. Cadmium in small mammals. Pages 377-388 in W.N. Beyer, G.H. Heinz, and A.W. Redmon-Norwood (eds.). Environmental Contaminants in Wildlife Interpreting Tissue Concentrations. CRC Press, Boca Raton, FL. 

Shore, R.F. and P.E.T. Douben. 1994. The ecological significance of cadmium intake and residues in terrestrial small mammals. Ecotoxicol. Environ. Safety 29 101-112. 

Proximity to the smokestacks of metal smelters is positively associated with increased levels of lead in the hair (manes) of horses and in tissues of small mammals, and is consistent with the results of soil and vegetation analyses (USEPA 1972). Lead concentrations were comparatively high in the hair of older or chronically impaired horses (USEPA 1972). However, tissues of white-tailed deer (Odocoileus virginianus) collected near a zinc smelter did not contain elevated levels of lead (Sileo and Beyer 1985). Among small mammals near a metal smelter, blood ALAD activity was reduced in the white-footed mouse but normal in others, e.g., the short-tailed shrew (Beyer et al. 1985). The interaction effects of lead components in smelter emissions with other components, such as zinc, cadmium, and arsenic, are unresolved (USEPA 1972) and warrant additional research. 

Cooke, J.A., S.M. Andrews, and M.S. Johnson. 1990a. Lead, zinc, cadmium and fluoride in small mammals from contaminated grassland established on fluorspar tailings. Water Air Soil Pollut. 51 43-54. 

Ma, W.C., W. Denneman, and J. Faber. 1991. Hazardous exposure of ground-living small mammals to cadmium and lead in contaminated terrestrial ecosystems. Arch. Environ. Contam. Toxicol. 20 266-270. 

Sheppard, C.R.C. and D.J. Bellamy. 1974. Pollution of the Mediterranean around Naples. Mar. Pollut. Bull. 5 42-44. Shore, R.F. 1995. Predicting cadmium, lead and fluoride levels in small mammals from soil residues and by species-species extrapolation. Environ. Pollut. 88 333-340. 

To protect humans and other mammals, proposed air-quality criteria range from 0.01 to less than 1.0 mg/m3 for metallic nickel and slightly soluble nickel compounds, 0.015-0.5 mg/m3 for water soluble nickel compounds, and 0.005 to 0.7 mg/m3 for nickel carbonyl (Table 6.10). Inhalation of nickel subsulfide concentrations (0.11 to 1.8 mg Ni/m3) near the current threshold limit value of 1 mg Ni/m3 can produce detrimental changes in the respiratory tract of rats after only a few days of exposure (Benson et al. 1995). Additional animal studies are recommended to identify minimally effective inhalation exposure levels for the various nickel compounds (USPHS 1993). Continued monitoring of nickel refining, nickel-cadmium battery manufacture, and nickel powder metallurgy installations is recommended because ambient air levels of bioavailable nickel at these... 

Cadmium Weak evidence for ultratrace essentiality in rats.7 Moderately toxic to all organisms a cumulative poison in mammals, causing renal failure possibly linked with hypertension in man. Has caused serous disease f ita] itai") in Japan from pollution. May also pose pollution problem associated with industrial use of zinc, e.g., galvanization. 

Metallothionein has been isolated from virtually all of the major mammal organs, including liver, kidney, brain, heart, intestine, lung, skin, and spleen. Nonlethal doses of cadmium, mercury, and lead induce synthesis of metallothionein. In test animals, nonlethal doses of cadmium followed by an increased level of metallothionein in the body have allowed later administration of doses of cadmium at a level fatal to nonacclimated animals, but without fatalities in the test subjects. 

Hunter BA, Johnson MS, Thompson DJ. 1987. Ecotoxicology of copper and cadmium in a contaminated grassland ecosystem. 3. Small mammals. J Appl Ecol 24 601-614. 

---