Cadmium-induced disturbances in lactating mammary glands of mice

Previous studies in various species have demonstrated that cadmium levels in milk are low and that cadmium is retained in the mammary glands of lactating rodents. The objective of the present study was to examine mammary glands following cadmium exposure during peak lactation. Mice were given 5 microg, 100 microg or 2000 microg cadmium/kg body weight subcutaneously on lactation days 8-10 and mammary glands were dissected on lactation day 11 for histology, quantitative gene expression and mineral analyses. Cadmium exposure induced morphological changes in the lactating mammary gland. A remodelling of the lactating mammary tissue including an increase in fat content, a less active feature of the mammary alveolar epithelial cells and more condensed appearance of the milk alveoli were observed. Although these changes were most prominent in the animals exposed to the highest cadmium dose similar morphological alterations were indicated at the two lower doses. A significant negative dose-response relationship between beta-casein gene expression and exposure of cadmium was demonstrated, while mRNA levels of alpha-lactalbumin were not affected by cadmium treatment. Furthermore, reduced levels of calcium in the mammary glands of the dams exposed to the highest cadmium dose and a positive correlation between calcium and beta-casein were demonstrated. No other differences were detected among the cadmium dose groups in mammary levels of calcium, zinc, iron or copper. In conclusion, our results indicate that cadmium disturbs the function of the lactating mammary gland, which consequently may impair the development of the suckling offspring.