ANTIOXIDANT ACTIVITY OF BRONCHOALVEOLAR LAVAGE FLUID IN THE ADULT RESPIRATORY-DISTRESS SYNDROME

Bronchoalveolar lavage (BAL) fluid from normal subjects is a potent inhibitor of lipid peroxidation. This antioxidant activity (AOA) of BAL fluid is primarily due to the serum proteins transferrin and ceruloplasmin. In the adult respiratory distress syndrome (ARDS), there is an influx of protein-rich edema fluid into the alveolar space that may increase antioxidant activity and provide protection against further oxidant-mediated lung injury. To test this hypothesis, the AOA of BAL fluid was measured in patients with ARDS (n = 11) and normal subjects (n = 12). When compared with normal subjects, BAL fluid from ARDS patients had a significantly higher concentration of total protein (2,536.8 +/- 408.2-mu-g/ml vs. 77.3 +/- 7.0-mu-g/ml, P < 0.005). When compared at several volumes, BAL fluid from ARDS patients was a more potent inhibitor of lipid peroxidation than BAL fluid from normals. In addition, when AOA was determined on equal milligram amounts of BAL fluid protein from ARDS patients and normal subjects, ARDS BAL fluid protein had a significantly higher AOA. Consistent with its higher AOA, ARDS BAL fluid contained increased concentrations of both transferrin (77.8 +/- 15.3-mu-g/ml vs. 2.78 +/- 0.3-mu-g/ml, P < 0.05) and ceruloplasmin (36.5 +/- 5.6-mu-g/ml vs. 0.26 +/- 0.02-mu-g/ml, P < 0.005) compared with normal subjects. The importance of both ceruloplasmin and transferrin in the enhanced AOA of ARDS BAL fluid was further demonstrated by studies that showed a significant decrement in AOA when the antioxidant functions of these two proteins were selectively blocked. These findings suggest that the BAL fluid in ARDS patients contains large amounts of serum proteins which possess antioxidant properties. Thus, the high permeability pulmonary edema of ARDS, although detrimental to gas exchange, may be beneficial in preventing further oxidant-mediated lung injury.