MURINE STRAIN DIFFERENCES AND THE EFFECTS OF ZINC ON CADMIUM CONCENTRATIONS IN TISSUES AFTER ACUTE CADMIUM EXPOSURE

The role of strain differences in cadmium tissue distribution was stud ied using sensitive (129/J) and resistant (A/J) mice. These murine str ains have previously been shown to differ in their susceptibility to c admium-induced testicular toxicity. Cadmium concentration was measured in testis, epididymis, seminal vesicle, liver, and kidney at 24 h aft er cadmium chloride exposure (4, 10, and 20 mu mol/kg CdCl2). The 129/ J mice exhibited a significant increase in cadmium concentration in te stis, epididymis, and seminal vesicle at all cadmium doses used, compa red to A/J mice. However, cadmium concentrations in liver and kidney w ere not different between the strains. at any dose, indicating that ca dmium uptake is similar in these organs at 24 h. These murine strains demonstrate similar hepatic and renal cadmium uptake but significantly different cadmium accumulation in the reproductive organs at 24 h. Th e mechanism of the protective effect of zinc on cadmium toxicity was s tudied by assessing the impact of zinc acetate (ZnAc) treatment on cad mium concentrations in 129/J mice after 24 h. Zinc pretreatment (250 m u mol/kg ZnAc), given 24 h prior to 20 mu mol/kg CdCl2 administration, significantly decreased the amount of cadmium in the testis, epididym is, and seminal vesicle of 129/J mice, and significantly increased the cadmium content of the liver after 24 h. Cadmium levels in the kidney were unaffected at this time. Zinc pretreatment also prevented the ca dmium-induced decrease in testicular sperm concentration and epididyma l sperm motility seen in 129/J mice. These findings suggest that the d ifferences in the two murine strains may be attributed partly to the d ifferential accumulation of cadmium in murine gonads. This may be caus ed by strain differences in the specificity of cadmium transport mecha nisms. The protective role of zinc in cadmium-induced testicular toxic ity in the sensitive strain may be due to an interference in the cadmi um uptake by susceptible reproductive organs.