Abstract
In order to study the placental transfer of mercury compounds (methylmercury and inorganic mercury), mercury-binding proteins in human placenta were examined by comparing with proteins binding with Zn, Cu, Cd, or Se, and the following results were obtained. 1) The human placenta supernatants were fractionated by Sephadex G-75 column. Zn was mainly bound to high molecular weight (mol. wt.) proteins, but Cu was observed in several mol. wt. ranges. Se was bound both to high and low mol. wt. proteins. Cd was primarily found in low mol. wt. fractions (metallothionein) with only a minute amount in high mol. wt. fractions. Zn and Cu concentration in umbilical cord blood was lower than that in maternal blood. 2) Inorganic mercury was bound both to high (void volume to 40000) and low (about 1100, metallothionein-like protein) mol. wt. proteins. Methylmercury bound to high mol. wt. proteins (void volume to 40000), but components of low mol. wt. (only a few thousands) were also observed. It was noted that methylmercury-binding proteins were differrent from inorganicmercury-binding proteins and, therefore, it was suggested that methylmercury compounds were more transferable across the placenta than inorganic mercury compounds.
