The placental transfer of cerium: experimental studies and estimates of doses to the human fetus from 141Ce and 144Ce.

Purpose : To measure the transfer of cerium from mother to fetus in experimental animals and estimate doses to the human fetus following intakes of radioisotopes of Ce. Materials and methods : Cerium-141 in chloride solution was administered intravenously to rats at different stages of pregnancy (days 9.5, 12.5 or 18.5), and retention in the embryo/fetus and associated tissues was measured 3 days later in each case. Retention in rat fetal tissues on day 21.5 (shortly before birth) was also measured after administration of 141 Ce chloride 1 month prior to conception or 141 Ce citrate on day 18.5. Cerium-141 chloride was administered to guinea pigs on day 50 for measurements of fetal retention on day 57 (shortly before birth). Results : Retention of 141 Ce in the rat embryo/fetus, measured at 3 days after administration to the mother, increased from about 0.00002% of injected activity per embryo/fetus on day 12.5 to about 0.014% on day 21.5 of gestation. However, the relative concentrations of 141 Ce in the...