The metabolism of metals in rat placenta.

The status and transfer of metals across the rat placenta were studied by subcellular and molecular fractionations of this organ at 2 and 24 h after iv injection of radiolabeled metals. The soluble and nuclear fractions showed higher contents of copper and zinc, whereas most of the nickel was associated with the soluble fraction. Cadmium was almost evenly distributed between the microsomal and nuclear fractions. Gel filtration of the soluble fractions showed nickel associated with an unknown low molecular weight form; zinc with high molecular weight proteins; copper with metallothionein, ceruloplasmin, and high molecular weight proteins; and cadmium with high molecular weight proteins and metallothionein.