The heavy metal cadmium is a widely distributed naturally occurring toxic element. Zinc and cadmium have striking physical and chemical similarities. The fact that they compete with each other for the same metallothionein makes their biological interactions very likely. In this study the effect of zinc deficiency on potentiating the pathologic effects of cadmium on the immune system and the kidneys were studied. Four week old C57BL6 male mice were fed zinc deficient diet (Zn 1 ppm) for 4 weeks, then cadmium 50 ppm was added to the drinking water, and after 3 weeks they were fed a regular chow diet. Animals were sacrificed at 0, 3 and 6 weeks after cessation of treatment. In other groups, 50 ppm zinc was added to the regular chow diet. -- The number of IgM and IgG antibody forming cells in the spleen was significantly lower after treatment with zinc-deficient diet compared to nontreated controls. Concurrent administration of cadmium antagonised that reduction. Proliferative response of spleen cells to the T cell-mitogen, phytohaemagglutinin decreased after treatment with zinc-deficient diet and cadmium administration tended to increase it. The number of CD4+ and CD8+ cells was decreased after treatment with zinc-deficient diet and a further reduction was observed after concurrent cadmium administration. Natural killer cell activity in the spleen decreased after treatment with zinc deficient diet. Concurrent cadmium administration caused more suppression. -- Simultaneous Treatment with zinc deficient diet and cadmium did not alter spleen, thymus and kidney weights and lymphocyte count. However, lymphocyte count in blood collected from the right atrium of the heart was significantly decreased in animals treated with zinc-deficient diet. -- On electron microscopic examination, kidneys of cadmium-treated mice showed ultrastructural alterations in the proximal tubular epithelial cells. However, animals treated with low zinc diets showed cellular degeneration mainly in the cortical area of the thymus. Zinc concentrations in the kidney tended to decrease after treatment with zinc-deficient diet. Cadmium concentrations increased after treatment with zinc-deficient diet and further increase observed after concurrent cadmium administration. -- INDEXING KEY WORDS: Cadmium; Zinc; Cellular Immunity
