EARLY ALTERATIONS IN INTRACELLULAR AND ALVEOLAR SURFACTANT OF THE RATLUNG IN RESPONSE TO ENDOTOXIN

The aim of this study was to characterize early ultrastructural, bioch emical, and functional alterations of the pulmonary surfactant system induced by Salmonella minnesota lipopolysaccharide (LPS) in rat lungs. Experimental groups were: (1) control in vitro, 150 min perfusion; (2 ) LPS in vitro, 150 min perfusion, infusion of 50 mu g/ml LPS after 40 min; (3) control ex vivo, 10 min perfusion; (4) LPS ex vivo, lungs pe rfused for 10 min from rats treated for 110 min with 20 mg/kg LPS intr aperitoneally. Morphometry of type II pneumocytes showed that LPS incr eased stored surfactant. Lamellar bodies were increased in size, but d ecreased in numerical density, suggesting that giant lamellar bodies o bserved in LPS-treated lungs may result from fusion of normal bodies. Structural analysis of alveolar surfactant composition showed that LPS elicited an increase in lamellar body-like and multilamellar forms. B ronchoalveolar lavage (BAL) material from LPS-treated lungs was decrea sed in phospholipids. BAL bubble surfactometer analysis showed a reduc tion in hysteresis area caused by LPS. We conclude that LPS leads to a lterations of intracellular and alveolar surfactant within 2 h: fusion of lamellar bodies, reduction in surfactant secretion, and changes in alveolar surfactant transformation, composition, and function, which may contribute to the development of respiratory distress.