HEARING AND GLYCOCONJUGATES - LOCALIZATION OF LE(Y), LE(X) AND SIALOSYL-LE(X) IN GUINEA-PIG COCHLEA, PARTICULARLY AT THE TECTORIAL MEMBRANE AND SENSORY EPITHELIA OF THE ORGAN OF CORTI

Immunohistological examination of guinea pig cochleas was performed using a panel of 25 monoclonal antibodies directed to various lacto-, ganglio- and globo-series carbohydrate epitopes as well as mucin-type epitopes. Lactoseries structures were found to be localized at specific sites of the tectorial membrane (TM) and Corti's organ, i.e. alpha1-->3 fucosyl type 2 chain (Le(x)) at Kimura's membrane, marginal band and covering net of TM; alpha1-->2,alpha1-->3 difucosyl type 2 chain (Le(y)) at covering net; and sialosyl-Le(x) and sialosyl-i at Kimura's membrane and sensory epithelia, particularly sensory tips of hair cells of Corti's organ. In striking contrast, ganglio-series structures (GM3, GD3, GD2, 9-O-Ac-GD3) were detected at spiral ganglion cells, neuronal fibres and stria vascularis, but were completely absent from Corti's organ and most of the TM. Other epitope structures defined by various antibodies were not detectable at any location. The functional roles of lacto-series carbohydrate epitopes expressed at TM and Corti's organ remain unknown. However, the expression of Le(y) (but not other structures) in association with developmental deficiency of TM induced by 6-N-propyl-2-thio-uracil in rats suggests that Le(y) plays some role in normal TM development. The presence of Le(x) at Kimura's membrane and sialosyl-Le(x) at hair cell sensory tips of Corti's organ suggests the intriguing possibility that these fucosylated/sialosylated carbohydrate structures play some role in interactions (either attractive or repulsive) of these inner ear components, which have been implicated in the physiology of hearing, i.e. the conversion of sound waves to nerve impulses.