FUNCTIONAL AND FINE-STRUCTURAL CHANGES IN ISOLATED RAT LUNGS CHALLENGED WITH ENDOTOXIN EX-VIVO, AND IN-VITRO

The aim of this study urns to relate changes in rat lung functions cau sed by the endotoxin lipopolysaccharide (LPS) to alterations in struct ure. The following four experimental groups were used 1), control in v itro, perfusion for 150 minutes; 2), LPS in vitro, perfusion for 150 m inutes and infusion of 5 mg of LPS after 40 minutes; 3), control ex vi vo, perfusion for 10 minutes; and 4), LPS ex vivo, lungs perfused for 10 minutes from rats treated for 110 minutes with 20 mg/kg LPS intrape ritoneally. Histologically, blood-derived leukocytes were detectable o nly in lungs from group 4, where neutrophils were found in capillaries , interstitium, and endothelial pouches. LPS treatment increased pulmo nary resistance and decreased pulmonary compliance in group 4 (ex vivo ), and to a greater extent, is group 2 (in vitro). In these two groups , formation of giant lamellar bodies in the type II pneumocytes was ob served. By histological examination, the bronchoconstriction induced b y LPS in vitro was localized to the terminal bronchioles. At 2 hours a fter LPS treatment, no edema and no change is precapillary and postcap illary resistance, capillary pressure, vascular compliance, capillary permeability, and the wet/dry ratio was observed. Thus, our major find ings are that LPS induced constriction of the terminal bronchioles in vitro,formation of giant lamellar bodies in type II pneumocytes ex viv o and in vitro, and trapping of neutrophils in endothelial pouches in vivo.