Inhibitory effect of zinc on nickel subsulfide carcinogenesis in Fischer rats

ATSDR evaluation of the health effects of zinc and relevance to public health

As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites, which have the greatest public health impact. These profiles comprehensively summarise toxicological and environmental information. This article constitutes the release of portions of the Toxicological Profile for Zinc. The primary purpose of this article is to provide public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective on the toxicology of zinc. It contains descriptions and evaluations of toxicological studies and epidemiological investigations, and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health. Toxicology and Industrial Health 2006; 22: 423-493.

Accumulation of zinc, nickel, lead and cadmium in some organs of rabbits after dietary nickel and zinc inclusion

This study reports the effect of dietary nickel (Ni) and a combination of Ni and zinc (Zn) on the accumulation of lead (Pb), cadmium (Cd), Ni and Zn in muscles, liver and kidneys of rabbits. Female rabbits (Oryctolagus cuniculus) of experimental groups were fed a granular mixture with addition of various concentrations of Ni or Ni+Zn (E1 - 17.5 g NiCl(2) per 100 kg of feed mixture, group E2 - 35.0 g NiCl(2) per 100 kg of feed mixture, group E3 - 17.5 g NiCl(2) per 100 kg of feed mixture and 30 g ZnCl(2) per 100 kg of feed mixture, group E4 - 35.0 g NiCl(2) per 100 kg of feed mixture and 30 g ZnCl(2) per 100 kg of feed mixture). Group C without inclusion of Ni or Zn served as control. After the 90-day experimental period biological material (liver, kidney, musculus longissimus dorsi, musculus biceps femoris) was taken from the animals. Samples were analyzed by the AAS method. Ni added to the FM caused an increase in Cd concentration in the kidneys of the rabbits, significantly in the E3 group in comparison with the control group. In the liver an insignificant decrease of Cd concentration was found. Zn addition in the amount of 30 g to the diet caused an increase of Cd level in the kidney as well as in the liver. Ni and Zn treatment caused a significant decrease of Pb accumulation in the m. longissimus dorsi of rabbits. This study indicates that dietary inclusion of Ni and Zn caused specific interactions among the observed metals.

Are metals dietary carcinogens?

Humans have been in contact with metals almost since the beginning of our existence. In fact, one cannot even think on human evolution without considering the great role played by metals in mankind's development. Metals are common moieties of molecules involved in a wide variety of biological processes, and hence are found in virtually all living organisms. Some metals are essential for human nutrition; others are found as contaminants in foodstuffs. One feature of the normal human diet which is frequently found is the simultaneous presence of both essential and toxic metals. Other factors important in the risk-evaluation analysis of metals are their pharmacokinetics, interactions among them and with other major components of the diet, and, especially, the great differences in the dietary habits of different populations and in the regional distribution of metals. In attempting to understand the role which dietary metals could play in human carcinogenesis, we found that the many factors involved and the lack of specific information made it difficult to reach firm conclusions on the hazards of dietary metals. We hope that this paper will raise the interest of genetic toxicologists in the subject and will consequently facilitate a risk analysis of the carcinogenic potential of dietary metals.

Localization of zinc and metallothionein in the rat bladder epithelium during carcinogenesis induced by N-butyl-N-(4-hydroxybutyl) nitrosamine

This study investigated the presence of zinc and expression of metallothionein (MT) in different pathological changes of the rat bladder induced by administration of N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). Using the Timm staining method, the presence of zinc was observed in normal and benign hyperplastic epithelial cells of the rat bladder, particularly in the malignant bladder tumor, induced by the administration of BBN. Immunohistochemically, MT expression was detected only in noninvasive (30%) and invasive transitional cell carcinoma (80%) of the rat bladder where the tumor cells were rich in zinc. Our data suggest that: (1) growth and development of the rat bladder tumor, especially malignant tumors, may have a high requirement for zinc and (2) MT synthesis may be induced by a high zinc concentration in rat bladder tumor cells.

The influence of zinc administration on the development of experimental lung metastases after an injection of tumour cells into the tail vein of rats

Rats having received drinking water enriched with zinc (zinc acetate, 22.8 mmol/l) developed significantly more pulmonal metastases after an i.v. injection of 5 x 10(5) cultivated cells of a benzpyrene-induced sarcoma than receiving normal drinking water. Zinc ions seem to promote the emigration, implantation and outgrowth of circulating tumour cells.