Physicochemical properties of avian tracheal mucus

Abstract

Dual-radiolabeled avian [chicken] tracheal secretions were obtained by giving Na235SO4 and D-[1-3H]glucosamine simultaneously into the lumen of the trachea in preparations in vitro. These secretions comprised fibrillar, gelatinous and soluble-phase mucins. These were eluted as single components in the non-retarded fractions from Bio-Gel A-15m. Although no evidence of the presence of subunit structure was found, chemical and radiolabeling analyses showed a high degree of internal inhomogeneity among the 3 types of mucins. The diferences among these mucins could be attributed to the chemical nature of their constituent glycoproteins. Glycoprotein fractions separated by ion-exchange chromatography contained sulfate and N-acetylneuraminic acid residues in differing amounts. Overall acidic properties appeared to be correlated with ester sulfate content. A close similarity in the carbohydrate composition and a reciprocal relationship between the total ester sulfate residue contents and 35S- and 3H-labeling suggested that, in addition to stepwise glycosylation and sulfation, some pre-existing sulfated oligosaccharides might have been utilized for the synthesis of acidic glycoproteins.