Cadmium uptake by the rat embryo as a function of gestational age.

Maternal blood, liver, kidney, and placental and fetal (embryo) accumulation of cadmium (Cd), a known embryotoxic trace element, was investigated following a single oral dose of various amounts of Cd (10 to 1,000 microgram/rat) as CdCl2 containing 109Cd at days 6, 10, 14, and 17 of gestation. Twenty-four hours after Cd administration the rats were killed and the various tissues were counted in a gamma well counter for determination of 109Cd activity. Maternal liver and kidneys were the main target organs of Cd accumulation at all stages of gestation. Embryo levels of Cd were highest prior to formation of the functional placenta. After placental formation, fetal Cd levels were decreased, while placental accumulation of Cd increased with increasing gestational age. The results indicate that the embryo accumulates the greatest percentage of ingested Cd between implantation and placentation, the early period of organogenesis. The placenta apparently protects the fetus from exposure to this element during the last third of gestation.