Effect of inorganic mercury on in vitro placental nutrient transfer and oxygen consumption

The effect of mercury (HgCl₂) on placental amino acid and glucose transfer as determined by the use of their nonmetabolizable radioactive analogues, aminoisobutyric acid (AIB) and 3-o-metyhl glucose (3MG), respectively, was studied in an in vitro perfusion model of a term human placenta. Hg²⁺ was found to decrease the transfer and accumulation of AIB without affecting 3MG transfer. It was also found to decrease the placental oxygen consumption rate. Placental circulation and tissue morphology remained intact, as demonstrated by the antipyrine transfer rate, and by electron microscopy, respectively. The mechanism by which Hg²⁺ may interfere with placental amino acid transfer and accumulation is discussed. Although much higher concentrations than those found in the ordinary polluted environment were used, this is the first report showing that Hg²⁺ interferes with an essential human placental function in a system employing a whole human placental cotyledon. This finding may indicate the possible involvement of Hg²⁺ in impaired organogenesis in early pregnancy or deranged fetal growth during the last trimester.