Foetal and Maternal Distribution of Inhaled Mercury Vapour in Pregnant Mice: Influence of Selenite and Dithiocarbamates

Abstract

The distribution of mercury after inhalation of metallic mercury vapour (6-8 mumols 203Hg0/kg b.wt.) was studied in pregnant mice (day 17 of gestation) after pretreatment with selenite (10 mumols Se/kg b.wt. intraperitoneally 1 hr before inhalation), thiram, disulfiram or diethyldithiocarbamate (1 mmol/kg orally 2 hr before inhalation of Hg0). For comparison, the effects of thiram, disulfiram and diethyldithiocarbamate on the distribution of mercury after administration of ionic mercury (7 mumols 203HgCl2/kg b.wt. intravenously) were also studied. Selenite pretreatment caused a longer retention of mercury in maternal tissues but decreased the foetal concentrations after 203Hg0 inhalation, similarly to what has been shown previously after administration of ionic mercury (Hg2+). Pretreatment with the three dithiocarbamates markedly increased the uptake in maternal brain and fat and decreased the foetal concentrations after intravenous injection of 203HgCl2. In contrast, no change in foetal uptake and only slight changes in maternal tissue concentration of mercury were observed after treatment with the dithiocarbamates followed by inhalation of 203Hg0, compared with 203Hg0 inhalation alone. The results are in favour of a firmer binding of mercury after Hg0 inhalation, when oxidation of Hg0 to Hg2+ occurs intracellularly, than after Hg2+ injection. Further studies, using repeatedly low dose administration of selenium, are needed to draw any conclusions concerning the protective effects of selenium after exposure to metallic mercury vapour.