Carbohydrate composition of stereociliary glycocalyx of the utricle of guinea pig inner ear

The carbohydrate composition of the stereociliary glycocalyx of the utricle was analysed quantitatively. The utricular sensory epithelium was collected from adult albino guinea pigs, and its apical surface structure was blotted onto a PVDF membrane, which was then subjected to acid hydrolysis. The hydrolysate was treated with 1-phenyl-3-methyl-5-pyrazolone for labelling and analysed by reversed-phase HPLC coupled with detection of W absorbance at 245 nm. Man, GlcN, GalN, Glc, Gal and Fuc were detected and estimated to be 211, 219, 46, 1,270, 266 and 36 pmoles per 10 utricular maculae, respectively. The presence of Man indicates the presence of N-linked glycoconjugates, and the considerable amounts of GlcN and Gal suggest the presence of complex-type N-glycosides, poly-lactosamine and/or keratan sulfate. The relatively low GalN content indicates that O-glycosides, chondroitin sulfates and GalNAc-containing glycosphingolipids, i.e. gangliosides and globosides, are minor components. Electronmicroscopic and confocal laser scanning microscopic observations revealed that the blotted apical surface structure constituted mostly the ciliary bundle. Consequently, the observed carbohydrate composition is probably that of the stereociliary glycocalyx of the utricular sensory epithelium.