Abstract
Pregnant and nursing rats were given water containing 1, 000ppm manganese (MnCl2 was used) ad libitum and the transfer of Mn to fetuses and sucklings was investigated. Administration of Mn during the first half of the gestation period before placentation produced no difference in Mn concentration in embryos, including chorions, from the control group. However, when Mn was administered during the second half of the gestation period, the fetal and placental concentrations of Mn were 2.7 and 1.9 times, respectively, as high as those in the control group, and the dams showed significantly higher Mn concentrations in the liver and kidney than the control group (p<0.01). It is, therefore, considered that Mn is more likely to transfer to fetuses when given after placentation than when given during the first half of the gestation period. During the period of lactation, a significant difference was found only between the Mn concentrations in the livers of dams of the control group and the treated group (p<0.01). Sucklings began to show increased concentrations of Mn in the stomach and intestinal tract on the 8th day after birth, and the total Mn content in the liver, kidneys, and whole body, excluding the stomach and intestinal tract, was four to seven times as high as that of the control group on the 20th day after birth. These results suggest that the transfer of Mn into sucklings via milk during lactation is much greater than that into fetuses during pregnancy.
