[Regional variations of the cytokeratin expression along the guinea pig cochlear turn]

Expression of cytokeratin (Ck) proteins in the guinea pig cochlea was examined using a recently developed immunohistochemical method for celloidin section. This method has allowed us to observe a whole cochlea with excellent morphological preservation in a visual field under the light microscope. Anti-Ck antibodies FIL-7 (AE-1, Signet Lab.) and NCL-CK19 (Novocastra Lab.) stained all supporting cells of the organ of Corti, in which pillar cells, Deiters' cells, Hensen's cells, and Boettcher's cells showed a strong reaction. The histochemical labeling of pillar and Deiter's cells showed a gradual increment from the base to the apex. The immunohistochemically stained area in Hensen's cells increased toward the apex, which was attributed mainly to the increase in both the number and size of Hensen's cells from the base to the apex. In an electron-microscopic examination, changes in histochemical labeling of Hensen's cells did not appear from the base to the apex. Close examination revealed that reaction precipitates were distributed along a filament structure which seemed to correspond to the cytokeratin filaments. These results suggest that the Ck filaments give elasticity and flexibility to the supporting cells in the organ of Corti and provide mechanical strength to the organ of Corti at the upper turns, which vibrate with larger amplitudes, and that the Ck filaments in the supporting cell must be of considerable importance as a tuning mechanism. Immunohistochemical labeling for Ck was also observed in the spiral prominence cells, outer sulcus cells, interdental cells, and Reissner's membrane. The positively stained area in the outer sulcus increased from the apex to the base.