Fetotoxicity of inorganic mercury in the mouse: distribution and effects on nutrient uptake by placenta and fetus.

Different aspects on the fetotoxicity of HgCl2 have been studied in vivo and in vitro and have been compared to earlier results with CdCl2, which is known to cause placental necrosis and fetal death. Hg has to be given in higher doses (20-25 mg/kg body weight) than Cd (3-4 mg/kg body weight) to cause fetolethality in late pregnancy in the mouse. It does not cause the typical signs of placental damage (congestion and bleedings) as does Cd. At a dose level of 15 mg/kg body weight, Hg reaches more than 10 times higher concentrations (approx. 5 times higher on a molar basis) in the fetus, while Cd (4 mg/kg body weight) on the other hand appears in the placenta at a double molar concentration as compared to Hg. In a chick, limb bud mesenchyme cell culture differentiating into chondrocytes, Hg and Cd were about equally effective in inhibiting cartilage-specific staining by alcian blue (ED50 approximately 1 microM). Due to the strong accumulation of Hg and Cd in the placenta, the effects of Hg on the placental and fetal uptake of four nutrients was studied. Hg caused a dose-dependent decrease in fetal radioactivity as compared to controls 4 hours after administration of 57Co-vitamin B12 to the mother. However, this effect was not as marked as for Cd. Hg, on the other hand, decreased fetal radioactivity after 14C-alpha-aminobutyric acid more than Cd did. Both elements decreased the fetal uptake of 65Zn, probably due mainly to a concomitant decrease in maternal serum concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)