Expression of glycoconjugates in rat cochlea during postnatal development

Cochlea is immature in rats at birth. It undergoes structural maturation postnatally, and achieves physiological competence two weeks later. Since glycoconjugates (GCs) play an important role in cell differentiation and organogenesis, it was of interest to study their distribution in rat cochlea from birth to 6 weeks of age. Temporal bones of Sprague-Dawley rats were fixed in cold 4% paraformaldehyde, 0.1% glutaraldehyde for 4-6h. The specimens of 2, 4, and 6 weeks old animals were decalcified in 3% EDTA for 5-7 days, dehydrated and embedded in paraffin. Deparaffinized sections were treated with 1% bovine serum albumin for 1h to block nonspecific staining. Sections were subsequently incubated with seven biotinylated lectin probes for 3h and avidin-biotin-peroxidase complex for 1h. Diaminobenzidine was used as chromogen. Specificity of lectin binding was determined by treating the sections with solutions of lecims preincubated with corresponding inhibitory sugars. Staining intensity varied among lectins and localization of reaction product exhibited disparity in different regions of the cochlea. The most striking difference was observed in nonsensory regions of the cochlea involved in ion transport. No variation was observed in the presence of reaction product for all lectins among the four age groups studied. These results suggest that expression of particular GCs is perhaps established earlier during cochlear development. However, qualitative and quantitative differences amone GCs do occur during functional maturation of cochlea.