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 over estimated as the result of rapid net diffusion of urea from tissues in to the bronchoalveolar lavage (BAL) fluid. This study established a pr otocol for rat BAL in a manner that minimizes this problem and then us ed this procedure to examine the edemagenic effects of ozone (0(3)) ex posure on ELF volume and the concentrations of ELF protein and albumin . One passage lavage with variable dwell times up to 30 s showed no di fference in recovered urea, protein, and albumin and ELF volume betwee n 0 and 4 s, but a progressive increase of each thereafter. The calcul ated concentrations of protein and albumin in ELF did not vary signifi cantly with dwell time. By increasing the number of lavage passages fr om one to three, the amounts of recovered urea, protein, and albumin a nd estimated ELF volume were increased with each passage. Again, the c alculated concentrations of protein and albumin in ELF did not vary ap preciably. When a single lavage passage and no added dwell time were u sed, 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 vo lume 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 exe rted 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 signifi cant effect. SDS-PAGE analysis showed that small serum proteins includ ing albumin were greatly enriched in lung BAL fluid of 1 ppm 0(3)-expo sed rats. These results demonstrate that movement of water and protein into the airspaces after 0(3) exposure is not strictly coupled and th at protein recovery by BAL should cautiously be used to indicate airsp ace edema as a result of 0(3) injury.