Effect of dental amalgam on rat gene expression profiles

Dental amalgam is a source of exposure to elemental mercury vapor in the general population, and possible health risks from this have been debated for a long time. Many studies have examined the relationship between dental amalgam fillings and the amount of mercury in organs, blood, urine and other tissues. However, adverse health effects from mercury accumulated in the tissues were not clear. Objectives: The aim of this study was to elucidate the effect of elemental mercury vapor exposure from dental amalgam fillings on gene expression profiles. Methods: Ten female Sprague-Dawley rats were randomly assigned to experimental and control groups (n=5). Each experimental group received four amalgam fillings under anesthesia. Six months later, all animals were terminated by bleeding from the right auricle of the heart under anesthesia and they were then transcardially perfused with normal saline solution for one hour. After perfusion, brain, liver and kidneys were removed and their gene expression patterns were examined using a DNA microarray containing 26,962 genes. The amount of mercury in each organ was also measured. Results: Compared with the controls, 2 genes (Atp1b3, Dnaja2) were found to be up-regulated (control > 2.0) and 1 gene (Tap1) was down-regulated (control < 0.5) in the brain, 2 genes (Actb, Timm23) were found to be up-regulated and 1 gene (Spink3) was down-regulated in the liver and 2 genes (Mgat5, RT1-Bb) were found to be up-regulated and 6 genes (Rara, Pias4, Tnfaip8, Slc2a4, Wdr12, Timm13) were down-regulated in the kidneys. The amounts of mercury in the experimental groups were higher than those of the controls. Conclusion: Results of the present study showed that mercury vapor release affected the genes in the organs of rats which received amalgam fillings.