Analyses of human tracheobronchial mucus from healthy subjects.

Tracheobronchial mucus was obtained from four healthy subjects by fibreoptic bronchoscopy. The material was fractionated by gel exclusion chromatography on a Sepharose CL2B column. One peak of optical density 280 nm was found in the excluded volume and another in the included volume suggesting that these contained the majority of the aromatic amino acids. Alcian Blue was used to precipitate acidic glycoproteins in each fraction. When the dye had been redissolved two peaks of optical density at 620 nm were detected, in the excluded and included volumes respectively, and these peaks corresponded with the absorbance at 280 nm. The elution profiles were similar to those given by mucins from other systems. Treatment with urea and dithiothreitol caused no change in the elution profile so there is no evidence that disulphide bonds link glycoprotein subunits in airway mucus from healthy subjects.