Immunohistochemical study for localization of G-protein and P-glycoprotein in the inner ear

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1.Patterns of immunostaining in the guinea pig cochlea using anti-G-protein (Gsalpha, Gialpha, Goalpha) antibodies were compared. Strongly positive staining against Gsalpha, Gialpha and Goalpha were observed in the outer hair cells, inner hair cells and stria vascularis. Immunoreactivity in the spiral ligament was light. In the cochlear nerve and spiral ganglionic fibers, immunoreactivity against Goalpha was strong but those against Gsalpha, Gialpha were light. Western blot analysis in cochlear tissue with the same antibodies used in the immunohistochemistry demonstrated a predominant 40 and 45 kDa proteins corresponding to the molecular mass of Gsalpha, 41 kDa protein for Gialpha and 39 kDa for Goalpha. From the present study, it was clarified that G-protein was abundant in the hair cells and stria vascularis and suggested that G-protein playd an important role in signal transduction of the cochlea.2.Expression of P-glycoprotein (P-gp) was detected in the guinea pig inner ear by immunohistochemical and Western immunoblot analyzes using mouse anti-P-gp monoclonal antibody C219. P-gp was found only in the capillary endothelial cells of the cochlea and vestibule. The pattern of P-gp immunostaining in the inner ear was similar to that of the brain. By Western immunoblot analysis, P-gp of 170 kDa was detected at a high level in isolated brain capillaries and at low levels in whole brain, lateral wall tissue of the cochlea, vestibular tissue and cochlear nerve in the modiolus. The present investigation suggested that P-gp expression in inner ear capillary endothelial cells might play an important role in the blood-inner ear barrier by acting as an extrusion pump.