Abstract
In order to investigate the cross placental transfer of particulate materials and their deposition in feto-placental unit, two kinds of 198Au-colloid solutions, 5 and 30 nm in particle diameter, were injected into pregnant rats at 19th day of gestation. The transferred rate to the fetus was very small, being approximately 0.018 and 0.005% for 198Au-colloid of 5 and 30 nm in diameter, respectively, of the administered dose per litter at 24 hours after injection. The concetration of colloidal gold in the fetus, fetal membranes and placenta was greater for 198Au-colloids of 5 nm in diameter than those of 30 nm. This fact may be attributed not to the particle size but to the difference between the average concentrations of these particles in the maternal blood. In view of the fact that the radioactivity of fetal membranes was as high as placental tissues, it is speculated that these particles were transferred to the fetus not only across the chorioallantonic placeta but also via the yolk sac placenta.
