Piriprost pretreatment attenuates the smoke-induced increase in ^99mtcDTPA lung clearance

We studied the effects of acute smoke exposure on lung permeability, eicosanoids, and inflammatory cell activity. Thirty-five New Zealand white rabbits were anesthetized, paralyzed, and exposed to 60 tidal volume breaths of diesel fuel-polycarbonate plastic smoke or sham smoke within 10 min. At 1 h postexposure the rabbits were killed and their lungs were removed for bronchoalveolar lavage (BAL) or pathologic procedures. Smoke exposure caused decreases in technetium-labeled diethylenetriamine pen-taacetate (^99mTcDTPA, mol. wt. 492 Da) biological half-life (t_1/2), BAL plasminogen activator, and BAL leukotriene B₄ (LTB₄). In addition, alveolar macrophage acid phosphatase enzyme activity increased in smoke-exposed rabbits. The leukotriene synthesis inhibitor, piriprost (U-60,257), given before smoke exposure, caused attenuation of the changes in ^99mTcDTPA uptake and plasminogen activator, swelling of type I alveolar cell epithelium, a large increase in lung inflammatory cells, and decreases in BAL LTB prostaglandin E₂ (PGE₂), and TxB₂ (stable metabolite of thromboxane, TxA₂). We conclude that changes in alveolar-capillary barrier permeability and plasminogen activator activity occur within 1 h after exposure to smoke and may play an early role in the inflammatory process associated with smoke inhalation injury. Furthermore, piriprost attenuates the smoke-induced increase in alveolar-capillary barrier permeability and decrease in plasminogen activator activity and causes a swelling of type I alveolar epithelium. However, our data suggest that neither lung eicosanoids or the alveolar macrophage lysis process plays a major role in the smoke-induced increase in alveolar-capillary barrier permeability.