Expression of p-glycoprotein is associated with that of multidrug resistance protein 1 (MRP1) in the vestibular labyrinth and endolymphatic sac of the guinea pig.

Expression of p-glycoprotein (p-gp) and multidrug resistance protein 1 (MRP1) was detected in the vestibular labyrinth and endolymphatic sac (ES) of the guinea pig by immunohistochemical staining using anti-p-gp monoclonal antibody (mAb) C219 and anti-MRP mAb MRPr1. P-gp was detected in capillary endothelial cells of the crista ampullaris, utricle, saccule and ES. MRP1 was detected in the epithelial lining of the crista ampullaris, utricle, saccule, and epithelial cells of the ES. Since p-gp and MRP1 act as extrusion pumps, they may coordinate with each other in vestibular organs and ES and play an important role in the blood-labyrinth barrier.