Biosynthesis of respiratory-tract mucins. Incorporation of radioactive precursors into glycoproteins by canine tracheal explants in vitro

Abstract

1. Canine tracheal explants, cultured in medium 199, actively incorporated radioactive precursors into secreted macromolecules in vitro. 2. Puromycin, 6-diazo-5-oxo-l-norleucine and ouabain markedly inhibited the incorporation of these precursors. 3. Exogenous glucosamine at concentrations above 20mm caused a greater than 50% inhibition of the incorporation of l-[G-(3)H]fucose and l-[U-(14)C]serine. 4. Carbohydrate content of the purified secretions was approximately 50% and consisted principally of galactose, N-acetylglucosamine, N-acetylgalactosamine, fucose and sialic acids. 5. Chromatography on DEAE-cellulose and Bio-Gel A-150m and equilibrium density-gradient centrifugation in a CsCl gradient confirmed the presence of mucous glycoproteins. 6. Electrophoresis on 1% agarose gels gave profiles that were identical with canine respiratory mucus obtained in vivo. 7. These results support the utility of the explant system for studies of respiratory secretions.

Lectin‐gold cytochemistry of mucin oligosaccharide biosynthesis in golgi apparatus of airway secretory cells of the hamster

“…Biochemical structures of airway mucin oligosaccharides have been reported in several mammalian species (Ellis and Stahl, 1973; Boat and Cheng, 1980;Lamblin et al, 1980;Rana et al, 1984). According to and Rana et al (1984), who have established the complete structure of swine tracheal mucin oligosaccharides, the variety of the chain length, have the following three structural features in common.…”

Comparison of mucus flow rate, radiolabelled glycoprotein output and smooth muscle contraction in the ferret trachea in vitro

“…Radiolabelled precursors are incorporated into proteoglycans as well as glycoproteins in human, canine (Coles et al, 1982) and rabbit explants, where they may be largely products of the cartilage and connective tissue . They may be present in secretions washed from normal human airways in vivo (Bhaskar et al, 1985) and canine airways in vitro (Bhaskar et al, 1986), although the latter result is disputed (Ellis & Stahl, 1973). It is not known if ferret tracheal explants produce proteoglycans.…”

Cellular and Molecular Biology of Airway Mucins

“…Beginning in the 1960s, several important descriptive studies utilized the alcian blue/PAS stain to identify mucosubstances in different regions of healthy and diseased airways (Lamb and Reid, 1969). By the 1970s, more mechanistic studies of mucus production were performed using bronchial or tracheal organ culture techniques (Ellis and Stahl, 1973; Boat et al, 1974). At this time, classical particle clearance physiologic techniques were used to investigate the flow of mucus over airway surfaces.…”