Lack of Active Transfer of 14 C Tetraethylammonium and Para-Aminohippuric Acid by the Term Sheep Placenta ∗

Abstract

Summary

The placental transfer of PAH and ¹⁴C TEA by term sheep placenta was evaluated by administration of each compound via the maternal and fetal circulations. A, which is transferred passively by the placenta, was used as a reference compound. We found that the placental transfer rates of PAH and TEA were very low bidirectionally. This observation is interpreted as virtually excluding an active transport mechanism for transfer of organic acids and bases from the fetal compartment to the maternal circulation. Data obtained following probenecid and cyanine 863 administration were consistent with this conclusion.