An extended substrate spectrum of the proton organic cation antiporter and relation to other cation transporters.

Most central nervous system (CNS) active drugs are organic cations, which need carrier proteins for efficient transfer through the blood-brain barrier (BBB). A genetically still unidentified proton organic cation (H/OC) antiporter is found in several tissues, including endothelial cells of the BBB. We characterized the substrate spectrum of the H/OC antiporter and the overlap in substrate spectrum with OCTN1, OCTN2 or OCT3 by screening 87 potential substrates for transport activity.