PROTEIN, CELL, AND LTB(4) CONCENTRATIONS OF LUNG EDEMA FLUID PRODUCEDBY HIGH CAPILLARY PRESSURES IN RABBIT

We previously demonstrated disruptions of the pulmonary capillary endo thelium and alveolar epithelium at transmural pressures (Ptm) of 52.5 cmH(2)O in rabbit by electron microscopy. In the present study, we det ermined the characteristics of the alveolar edema fluid in this condit ion by carrying out bronchoalveolar lavage after blood perfusion for 1 0 min at Ptm of 12.5 (low), 32.5 (intermediate), and 52.5 cmH(2)O (hig h). At low Ptm, where our previous studies showed no ultrastructural c hanges, the volume of alveolar fluid obtained by urea dilution was ver y small, and the concentrations of proteins, cells, and leukotriene B- 4 (LTB(4)) in the bronchoalveolar lavage fluid (BALF) were low. Howeve r, at high Ptm the volume of alveolar fluid and the concentrations of total protein and cells in the BALF were greatly increased. The amount of LTB, in the BALF also increased substantially from 6.0 to 49.5 mu g (P < 0.001). Intermediate changes were seen at intermediate Ptm. We concluded that exposing pulmonary capillaries to high Ptm results in a high-permeability form of edema. In addition, the presence of LTB(4) suggests that chemical mediators are released, possibly as the result of exposure of the reactive capillary endothelial basement membrane, a s demonstrated by electron microscopy.