Maternal-fetal distribution of manganese in the rat following inhalation exposure to manganese sulfate.

Abstract Studies examining the pharmacokinetics of manganese during pregnancy have largely focused on the oral route of exposure and have shown that the amount of manganese that crosses the rodent placenta is low. However, limited information exists regarding the distribution of manganese in fetal tissues following inhalation. The objective of this study was to determine manganese body burden in CD rats and fetuses following inhalation of a MnSO 4 aerosol during pregnancy. Animals were evaluated following pre-breeding (2 weeks), mating (up to 14 days) and gestational (from gestation day (GD) 0 though 20) exposure to air or MnSO 4 (0.05, 0.5, or 1 mg Mn/m 3 ) for 6 h/day, 7 days/week. The following maternal samples were collected for manganese analysis: whole blood, lung, pancreas, liver, brain, femur, and placenta. Fetal tissues were examined on GD 20 and included whole blood, lung, liver, brain, and skull cap. Maternal lung manganese concentrations were increased following exposure to MnSO 4 at ≥0.05 mg Mn/m 3 . Maternal brain and placenta manganese concentrations were increased following exposure of pregnant rats to MnSO 4 at ≥0.5 mg Mn/m 3 . Increased fetal liver manganese concentrations were observed following in utero exposure to MnSO 4 at ≥0.5 mg Mn/m 3 . Manganese concentrations within all other fetal tissues were not different from air-exposed controls. The results of this study demonstrate that the placenta partially sequesters inhaled manganese, thereby limiting exposure to the fetus.