Recombinant tumor necrosis factor increases pulmonary vascular permeability independent of neutrophils

We studied the effects of intravenous infusion of recombinant human tumor necrosis factor type alpha (rTNF-alpha; 12 micrograms/kg) on lung fluid balance in sheep prepared with chronic lung lymph fistulas. The role of neutrophils was examined in sheep made neutropenic with hydroxyurea (200 mg/kg for 4 or 5 days) before receiving rTNF-alpha. Infusion of rTNF-alpha resulted in respiratory distress and 3-fold increases in pulmonary arterial pressure and pulmonary vascular resistance within 15 min, indicating intense pulmonary vasoconstriction. Pulmonary lymph flow (i.e., net transvascular fluid filtration rate) and transvascular protein clearance rate (a measure of vascular permeability to protein) increased 2-fold within 30 min. The increased permeability was associated with leukopenia and neutropenia. The pulmonary hypertension and vasoconstriction subsided but fluid filtration and vascular permeability continued to increase. Sheep made neutropenic had similar increases in pulmonary transvascular fluid filtration and vascular permeability. rTNF-alpha also produced concentration-dependent increases in permeability of 125I-labeled albumin across ovine endothelial cell monolayers in the absence of neutrophils or other inflammatory mediators. The results indicate that rTNF-alpha increases pulmonary vascular permeability to protein by an effect on the endothelium.