DIFFERENTIAL-EFFECTS OF OZONE ON LUNG EPITHELIAL LINING FLUID VOLUME AND PROTEIN-CONTENT

Urea dilution ha been used to estimate the volume of epithelial lining fluid (ELF) in the respiratory tract. However, ELF volume may be overestimated as the result of rapid net diffusion of urea from tissues into the bronchoalveolar lavage (BAL) fluid. This study established a protocol for rat BAL in a manner that minimizes this problem and then used this procedure to examine the edemagenic effects of ozone (0(3)) exposure on ELF volume and the concentrations of ELF protein and albumin. One passage lavage with variable dwell times up to 30 s showed no difference in recovered urea, protein, and albumin and ELF volume between 0 and 4 s, but a progressive increase of each thereafter. The calculated concentrations of protein and albumin in ELF did not vary significantly with dwell time. By increasing the number of lavage passages from one to three, the amounts of recovered urea, protein, and albumin and estimated ELF volume were increased with each passage. Again, the calculated concentrations of protein and albumin in ELF did not vary appreciably. When a single lavage passage and no added dwell time were used, it war observed that exposure of rats to 2 but not 0.5 and 1 ppm 0(3) increased urea, protein, and albumin in the BAL immediately after 6 h exposure. In addition, at 18 h postexposure to 1 ppm 0(3), ELF volume increased only 21%, but protein and albumin concentrations in ELF were 2.3- and 4.5-fold of control values, respectively. A higher 0(3) concentration (2 ppm) moderately increased ELF volume (+ 83%) and exerted even greater effects on concentrations of ELF protein (7.8-fold) and albumin (19-fold) while lower 0(3) dosage (0.5 ppm) had no significant effect. SDS-PAGE analysis showed that small serum proteins including albumin were greatly enriched in lung BAL fluid of 1 ppm 0(3)-exposed rats. These results demonstrate that movement of water and protein into the airspaces after 0(3) exposure is not strictly coupled and that protein recovery by BAL should cautiously be used to indicate airspace edema as a result of 0(3) injury.