GLYCOLIPIDIC COMPONENT OF THE EPITHELIAL-CELL COAT OF THE ENDOLYMPHATIC SAC

The endolymphatic sac (ES) is thought to synthesize and secrete glycoc onjugates such as sulfated glycoproteins into the endolymphatic lumen. Ganglioside Gm1 is a specialized glycolipid containing one sialic aci d molecule, which is generally found in the outer leaflet of the cell membrane. This glycolipid, which is known to be a specific receptor fo r cholera toxin (CT), acts as a membrane transducer and is involved in the modulation of cell metabolism, growth and regeneration. In the pr esent study we identified Gm1 by studying the distribution of the FITC -labeled CT-subunit B in the ES epithelium of adult guinea pigs. Our f indings indicate the presence of this ganglioside in the ES, with a pr edominant localization in the basolateral aspect of the epithelial cel l layer. No detectable differences between ES cell types could be iden tified, whilst the ES distal and intermediate portions showed more rea ctivity than the proximal portion. This study, which represents the fi rst description of a lipidic glycoconjugate component in the ES, provi des evidence in support of the role of the ES in the turnover and regu lation of inner ear fluids.