Disposition of inorganic mercury in pregnant rats and their offspring

Environmental toxicants such as methylmercury have been shown to negatively impact fetal health. Despite the prevalence of inorganic mercury (Hg(2+)) in the environment and the ability of methylmercury to biotransform into Hg(2+), little is known about the ability of Hg(2+) to cross the placenta into fetal tissues. Therefore, it is important to understand the handing and disposition of Hg(2+) in the reproductive system. The purpose of the current study was to assess the disposition and transport of Hg(2+) in placental and fetal tissues, and to test the hypothesis that acute renal injury in dams can alter the accumulation of Hg(2+) in fetal tissues. Pregnant Wistar rats were injected intravenously with 0.5 or 2.5 μmol kg(-1) HgCl2 for 6 or 48 h and the disposition of Hg(2+) was measured. Accumulation of Hg(2+) in the placenta was rapid and dose-dependent. Very little Hg(2+) was eliminated during the initial 48 h after exposure. When dams were exposed to the low dose of HgCl2, fetal accumulation of Hg(2+) increased between 6h and 48 h, while at the higher dose, accumulation was similar at each time point. Within fetal organs, the greatest concentration of Hg(2+) (nmol/g) was localized in the kidneys, followed by the liver and brain. A dose-dependent increase in the accumulation of Hg(2+) in fetal organs was observed, suggesting that continued maternal exposure may lead to increased fetal exposure. Taken together, these data indicate that Hg(2+) is capable of crossing the placenta and gaining access to fetal organs in a dose-dependent manner.