MARKERS OF MUCUS SECRETION AND DNA LEVELS IN INDUCED SPUTUM FROM ASTHMATIC AND FROM HEALTHY-SUBJECTS

To determine whether markers of mucus secretion can be quantified in a irway lining fluid from asthmatic and from healthy subjects, we measur ed levels of a mucin-like glycoprotein (MLG) and lactoferrin in sputum induced by inhalation of hypertonic (3%) saline in 18 asthmatic and i n 10 healthy subjects. Because DNA, like mucin, contributes to the vis cosity of airway secretions, we also measured DNA levels in the induce d sputum samples. To control for the presence of saliva in sputum, we also analyzed saliva samples from all subjects. The entire sputum samp le and the saliva sample were reduced using dithiotreitol, and biochem ical analysis was performed on supernatants obtained after centrifugat ion. We found that induced sputum from asthmatic subjects had higher l evels of MLG [2,574.4 +/- 907.8 (mean +/- SEM) versus 562.2 +/- 90.5 m ug/ml, p < 0.007] and DNA (7.1 +/- 1.6 versus 3.6 +/- 0.6 mug/ml, p < 0.05), but the difference in lactoferrin levels failed to reach statis tical significance. However, in the subgroup of asthmatic subjects who gave a history of sputum production (n = 9), lactoferrin levels were higher than in the healthy control subjects (118.9 +/- 46.3 versus 35. 2 +/- 6.5 gg/ml, p < 0.05). The very low levels of MLG, DNA, and lacto ferrin measured in saliva were not significantly different in asthmati c subjects from those in healthy subjects. We conclude that measuremen t of markers of mucus secretion in induced sputum is feasible in asthm atic and healthy subjects, and it reveals abnormally high markers of m ucus secretion in subjects with stable asthma. In these asthmatic pati ents the sputum DNA levels were much lower than those reported in sput um from patients with cystic fibrosis or bronchiectasis.