Localization of the Organic Anion Transporting Polypeptide 2 (Oatp2) in Capillary Endothelium and Choroid Plexus Epithelium of Rat Brain

Abstract

In this study we investigated the distribution of a recently cloned polyspecific organic anion transporting polypeptide (Oatp2) in rat brain by nonradioactive in situ hybridization histochemistry and immunofluorescence microscopy. The results demonstrate that Oatp 2 is expressed in brain capillary and in plexus epithelial cells. At the blood-brain barrier (BBB), Oatp 2 expression could be co-localized with the endothelial marker vWF (von Willebrand factor) but not with the astrocyte marker GFAP (glial fibrillary acidic protein). In choroid plexus epithelial cells, Oatp 2 could be localized to the basolateral cell pole, whereas the first member of the Oatp gene family of membrane transporters to be cloned (Oatp 1) co-localized with the α 1 subunit of Na,K-ATPase at the apical plasma membrane domain. Because Oatp 1 and Oatp 2 have been previously shown to mediate transmembrane transport of a wide variety of amphipathic organic compounds, including many drugs and other xenobiotics, the histochemical localization of Oatp 2 at the BBB and of Oatp 1 and Oatp 2 in the choroid plexus imply a role for these transporters in the active exchange of amphipathic solutes between the blood, brain, and cerebrospinal fluid compartments.