Comparison of some biochemical effects of teratogenic doses of mercuric mercury and cadmium in the pregnant rat.

Mercuric mercury (Hg2+), like cadmium (Cd2+), interferes with the transport of certain essential metals to the conceptus in the pregnant Wistar rat and, at 48 h after the IV injection of a teratogenic dose (0.79 mg Hg2+/kg body weight) on day 12 of gestation, the foetal concentrations of Zn2+, Cu2+ and Fe3+, but not of Mg2+, are reduced significantly. Both Hg2+ and Cd2+, at teratogenic dose levels, inhibit the placental and foetal uptake of 65Zn2+ and 67Cu2+, but possibly by different mechanisms. In addition, the effects of Hg2+, at different times after dosing, on the uptake of these labelled tracers and of 59Fe3+, administered as 15-min pulses, do not parallel the changes in the placental and foetal concentrations and contents of the endogenous, stable metallic ions. The teratogenic dose of Hg2+ inhibits the placental and foetal uptake of L-[4,5-3H]-leucine, but not the incorporation of the labelled amino acid into foetal protein. In contrast, the corresponding dose of Cd2+ inhibits both leucine uptake and protein synthesis in the placenta and foetus. Similarly, Cd2+ inhibits the uptake of [2-14C]-thymidine and its incorporation into foetal DNA, whereas Hg2+ reduces the placental and foetal uptake, but has little or no effect on the utilization of the nucleoside. Since both Cd2+ and Hg2+ reduce the foetal uptake of 65Zn and the foetal concentration of Zn, but only Cd2+ interferes with DNA synthesis, it is unlikely that the inhibition of the metabolism of thymidine can be attributed to reduction in thymidine kinase activity in consequence of foetal Zn deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)