The cell coat of inner ear sensory and supporting cells as demonstrated by ruthenium red

The ultrastructure of the cell coat of sensory and supporting cells of chinchilla and lizard inner ears was studied using ruthenium red. On the apical surface of both cell types, in both animals, the glycoproteins in the cell coat stain positively with this cationic dye. The apical surface of the sensory hair cells displays no regional variations in cell coat thickness. The uniform staining along the length of the stereocilia is not influenced by the normal presence or absence of a tectorial membrane. Although no micro-domains in the glycoproteins that stain positively with ruthenium red were observed that might correlate with the ultrastructural localization of sites of initiation of the transduction event, the cell coat material on the apical cell surface might play an important role in sequestering ions (particularly calcium) which are required for the transduction process.