Background: The majority of drugs cross epithelial cells by either passive diffusion or via carrier-mediated drug transporters. The aim of this study was to investigate the transport characteristics, protein expression and localization of organic cation transporters in human nasal epithelium.
Methods & results: The expression, localization and transport characteristics of the transporters were investigated using permeation, PCR and immunohistochemistry. The uptake of 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide followed Michaelis-Menten kinetics. Its intracellular accumulation of the compound was inhibited by organic cation transporters (OCTs) and carnitine/organic cation transporter (OCTNs) inhibitors. Detected OCT1-3, OCTN1 and OCTN2 gene transcripts correlated with immunohistological staining for OCT1-3, OCTN1 and OCTN2 antibodies. Except for OCTN1, the antibodies were generally localized on the apical side of the epithelial cells.
Conclusion: Based on the immunohistochemical and uptake/transport studies, we conclude that the human nasal epithelium expresses OCT1-3, OCTN1 and OCTN2 transporters mainly on the apical side of the nasal cells.