Distribution of ABC-transporters, organic anion/cation transporters and organic anion transporting polypeptide expression in the BECs (A) and in the CP epithelium (B). Members of the ABC family are presented in red, while SLC members are presented in various tones of blue. Some data indicate that in the BECs Mrp1 and P-gp may also be present in organelles and nuclear envelope. Membrane localization of Mrp1 in BECs is not completely clear, with some reports indicating that it is present at the luminal side, while others indicating that it is scarce and probably located at the abluminal side. Mrp5 was detected in the CPE cells at the transcript level, but there are no functional or immunocytochemical data so far, indicating its cellular localization (asterisk). The same stands for Oat2, Oct1-3 and Oatp9.