Expression and localization of drug transporters in the placenta. Transporters are shown as green symbols, and the arrows indicate the direction of the transport, if reported.BCRP, breast cancer resistance protein; MATE, multidrug and toxin extrusion; MRP, multidrug resistance-associated protein; OAT, organic anion transporter; OATP, organic anion transporting polypeptide; OCT, organic cation transporter; OCTN, organic cation/carnitine transporter; P-gp, P-glycoprotein.