Localization of fatty acid binding proteins (FABPs) in the cochlea of mice

Various fatty acids (FAs) are involved in many different functions in the organism as a source of energy, as essential ingredients of membranous lipids as well as intracellular signaling molecules. Intracellular fatty acid binding proteins (FABPs) comprise a family of soluble lipid binding proteins with low molecular masses and which can make long chain FAs soluble to allow intracellular translocation in the aqueous cytosol. To clarify the possible involvement of FAs and FABPs in hearing function, the present study investigated the localization of FABPs in the cochlea of adult mice using immunohistochemical procedures. Among various FABP species, H (heart-type)-FABP was localized in inner and outer pillar cells and outer phalangeal cells, while B (brain-type)-FABP was localized in border cells and cells of Hensen, and fibrocytes in the spiral limbus and spiral prominence. In the spiral ganglion, moderate to low H-FABP immunoreactivity was observed in almost all neurons, while B-FABP immunoreactivity was found in satellite cells. The discrete localization of the two FABPs in different non-receptor cells in the Organ of Corti suggests that the FABP species and/or their ligands, FAs, play important roles in the regulation of the hearing function.