The effect of cadmium on chemical‐ and viral‐induced tumor production in mice

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Abstract
Female Swiss mice were exposed to cadmium in the drinking water at concentrations ranging from 0 to 50 ppm for 105 or 280 day time periods. In the 105 day study, the effect of cadmium on urethan‐induced pulmonary adenoma formation was evaluated. Urethan‐induced sleeping times observed following i.p. injection of urethan after 3 weeks of cadmium exposure were not affected by cadmium indicating that chronic cadmium exposure did not alter the eliminaton of urethan. Pulmonary adenoma formation which was evaluated 84 days later was not affected by cadmium. The size and number of tumors remained unchanged. This suggests that the immunosuppressive actions of cadmium do not influence urethan‐induced adenoma formation. In the 280‐day study, the effects of cadmium on the incidence of spontaneous murine lymphocytic leukemia was evaluated. Mortality from the leukemia virus was greater in the cadmium‐exposed mice. Mice exposed to 10 or 50 ppm cadmium experienced 33% more deaths from the virus. The average time till death was unaffected. It appears that the immunosuppressive effects of cadmium impair immunosurveillance mechanisms that control expression of the murine lymphocytic leukemia virus.