Relationship between bronchoalveolar lavage neutrophil numbers and lavage fluid elastase and antielastase activities

Elastase and antielastase activities were measured in bronchoalveolar lavage fluid (BALF) and their relationship to bronchoalveolar lavage (BAL) neutrophil numbers was assessed in order to determine whether the elevated BAL neutrophil count can predict a shift in the elastase/antielastase balance. BAL samples were obtained from 133 randomly selected patients undergoing diagnostic bronchoscopy with BAL. Elastase and antielastase activities were determined using the synthetic substrate MeO-Suc-Ala-Ala-Pro-Val-pNA. In a random subset of 24 samples, the antioxidant capacity was measured as the inhibition of peroxyl radical-mediated oxidation of B-phycoerythrin. Only 7 of the BAL samples exhibited measurable elastase activity and all but one of these had a BAL neutrophil count greater than 100 x 10(3)/ml. Antielastase activity was measurable in 124 samples exhibiting no free elastase activity. There was a tendency for lower antielastase activity to be associated with higher neutrophil numbers, but this did not translate into a statistically significant correlation over all samples. There was no significant correlation between antioxidant capacity and either the neutrophil number or antielastase activity. It is concluded that BAL neutrophil numbers do not, in general, predict the status of elastase/antielastase balance in the epithelial lining fluid and that the antioxidant mechanisms in the epithelial lining fluid do not appear to be related to the antielastase capacity.