An experimental study on silver in the nervous system and on aspects of its general cellular toxicity.

Exposure of foetal and adult rats to silver results in a long-lasting deposition of the metal in many structures of the nervous system. A brief anatomical description of the localization of silver deposits as they are visualized by autometallography is provided. The consequences of silver in the nervous system were evaluated by volumetric measurements on developing rat hippocampi which showed that silver induced a decrease in the total volume of hippocampal pyramidal cells. The toxicity of silver at the cellular level was studied in a test-system of cultured macrophages. High doses of silver caused coagulation necrosis, whereas lower concentrations resulted in a cytotoxic and possibly a cytostatic effect without affecting cell structure. The processing of silver which resulted in lysosomal accumulations was affected by the metal itself in a dose-dependent fashion (autointerference). Other basic macrophage functions (protein-production, phagocytosis, migration) were not affected by silver at concentrations which did not cause acute cell death. Biochemically, silver causes an increase in lipid peroxidation, which was evident only in liver tissue. Coagulation necrosis and, to some extent, long-term effects on cell viability could be reversed by inorganic selenium, which was tested as a detoxicant. On the other hand, pre-exposure of animals to selenium greatly enhanced the silver-induced lipid peroxidation. Furthermore, the co-exposure to silver and nickel resulted in a synergistically increased lipid peroxidation.