Overview of Drug Transporters in Human Placenta

Abstract

The transport of drugs across the placenta is a point of great importance in pharmacotherapy during pregnancy. However, the knowledge of drug transport in pregnancy is mostly based on experimental clinical data, and the underlying biological mechanisms are not fully understood. In this review, we summarize the current knowledge of drug transporters in the human placenta. We only refer to human data since the placenta demonstrates great diversity among species. In addition, we describe the experimental models that have been used in human placental transport studies and discuss their availability. A better understanding of placental drug transporters will be beneficial for the health of pregnant women who need drug treatment and their fetuses.

Keywords: drug transporters; membrane transporters; placenta; placental transport; pregnancy; trophoblasts.

Figure 1

Human placental structure (above) and localization of drug transporters in human placenta (below). The blue arrows indicate the efflux direction, while the yellow arrows indicate the uptake direction in regard to the specifically shown cell type or compartment. The actual drug transport direction (discharge from placenta into the maternal circulation or uptake into placenta and fetal circulation) depends on the localization of the transporters. The transport direction is indicated by blue arrows for discharge and yellow arrows for uptake. Transporters in the fetal capillary are indicated by pink double-headed arrows because they may work in both directions depending on their exact localization in endothelium. The symbol “Φ” indicates a localization where the respective transporter does not exist. No symbols and no arrows mean that information is not available. The question mark symbol “?” shows that conflicting information exists.