Expression of multidrug resistance protein 1 (MRP1) in the rat cochlea with special reference to the blood-inner ear barrier.

Expression of multidrug resistance protein 1 (MRP1) was detected in the rat cochlea by RT-PCR and immunohistochemistry using anti-MRP monoclonal antibody MRPr1. Use of primers specific for rat mrp1 gene resulted in the amplification of an expected 394 bp fragment prepared from brain and cochlear tissues. Immunohistochemically, MRP was found in the choroid plexus, stria vascularis, spiral ligament, spiral prominence and cochlear nerve in the modiolus. From these results, it was suggested that MRP in the rat cochlea might function as an extrusion pump and play an important role in the blood-inner ear barrier.