Cadmium distribution and toxicity in tissues of small rodents

The aim of the present paper is to discuss the accumulation and distribution of cadmium (Cd) in the various tissues of animals, the interactions of cadmium with other elements, and the damage to tissues caused by this metal. Cadmium is not physiologically or biochemically essential to an organism. It is absorbed via the gastrointestinal tract and lungs and accumulated in various tissues, mainly the kidneys and liver. The distribution of cadmium between various tissues depends on many endogenous and exogenous factors. Cadmium is bound to a low-molecular-weight protein, metallothionein (MT), and to high-molecular-weight proteins. This metal has a great affinity to thiol groups. Cadmium binds also to O- and N-containing ligands. The distribution of cadmium between organs differs markedly depending on the chemical form of administered Cd and the duration of exposure. Acute exposure results in a different distribution pattern throughout the body than does chronic exposure. Long-term exposure to high doses of cadmium may cause biochemical and functional changes in some critical organs. Cadmium can influence the absorption and distribution of essential elements and can replace them in enzymes. Metallothionein and glutathione play important roles in the transport of metals and in detoxification processes. Reported findings are mainly the results of experiments on laboratory animals. The lack of data concerning the localization of cadmium in various tissues of wild species is noticeable and there is a great need for such data.