Characterization and Immunohistochemical Localization of the Glycoconjugates of the Rabbit Bladder Mucosa

Abstract

An impairment of the mucosal glycoconjugates could be an important factor in the development of bladder disorders such as interstitial cystitis. However, very little definitive biochemical information is available on the glycoconjugate components of the mammalian bladder mucosa. In this study, the mucosa from metabolically radiolabeled rabbit bladder was separated, delipidated, and digested with protease, and the released glycosaminoglycans and glycopeptides were fractionated. About 80 and 36% of the nondialyzable tritium and35S activities, respectively, was associated with the sialoglycopeptide fractions. The balance of the total tritium activity in the protease digest was in glycosaminoglycans identified as hyaluronan, chondroitin sulfates, and heparan sulfate. Immunohistochemical examination using anti-heparan sulfate antibodies, including one against mouse syndecan-1, indicated the presence of heparan sulfate proteoglycan in the epithelium. In contrast, there was no significant staining of the bladder epithelium with anti-chondroitin-4- and 6-sulfate antibodies or hyaluronan-binding protein. The lamina propria and muscle layers showed strong staining with anti-chondroitin-4-sulfate antibody and hyaluronan-binding protein and weak staining with anti-chondroitin-6-sulfate antibody. The insignificant levels of glycosaminoglycans in the glycocalyx of bladder mucosa epithelium suggest that glycosaminoglycans may be less important than other glycoconjugates in maintaining normal epithelial function and in bladder disorders such as interstitial cystitis.