Biochemical analysis of airway aspirates of newborns

We measured contents of tracheobronchial and alveolar components contained in the newborn airway aspirates (NAA) obtained from 54 healthy newborns, with bronchoalveolar lavage fluid (BALF) and bronchial lavage fluid (BLF) from healthy adults, and with mucoid sputum from adults with chronic bronchitis as controls. Fucose (a parameter of tracheobronchial mucus mucoprotein) and tryptase activity were used as tracheobronchial components, and pulmonary surfactant apoprotein A (SP-A) as an alveolar component. The ratio of the content of each component to that of total protein (TP) was compared among NAA, BLF, BALF, and the mucoid sputum. The SP-A/TP ratio in the NAA was similar to that in BLF but 1/24 of that in BALF. The fucose/TP ratio in NAA was about 1/2 of that in BLF and about 6 times higher than that in BALF. The tryptase/TP ratio in NAA was about twice that in BLF and about 80 times that in BALF. The ratios of the above components to TP in the mucoid sputum were closer to those in NAA and BLF than those in BALF. These results suggest that NAA contain both tracheobronchial and alveolar components, and their contents of the formers are larger than those of the latters, and that NAA may be useful for diagnosing pathologic conditions in the airway of newborns, and for comparing the biological defence mechanism between newborns and adults.