ALTERATIONS IN SURFACTANT NEUTRAL LIPID-COMPOSITION DURING THE DEVELOPMENT OF BLEOMYCIN-INDUCED PULMONARY FIBROSIS

The purpose of this investigation was to correlate changes in the neut ral lipids of pulmonary surfactant with previously observed changes in surfactant phospholipids and lung compliance in the rat model of bleo mycin-induced pulmonary fibrosis. Bronchoalveolar ravage fluid (BAL) o btained at 0, 1, 3, 7, 14, 30 and 120 days after transtracheal instill ation of bleomycin was used as a source of surfactant lipids. The mean concentration of neutral lipids in normal BAL a as 439 nmol/lung and was composed of 55% cholesterol (CHO), 27% cholesterol ester (CE) and 19% free fatty acids (FFA). CHO was elevated at 1 day, reaching a maxi mum 4-fold increase in concentration at 14 days before subsiding to no rmal at 120 days. In contrast to CHO, CE and FFA were significantly re duced at 1 day after bleomycin with FFA below detectable levels. Howev er, both these species were twice normal levels at 3-30 days before re turning to normal at 120 days. The fatty acid composition of CE did no t change; however, unsaturated fatty acids were significantly increase d in FFA between 3 and 120 days. The data indicate that there are sign ificant alterations in the neutral lipid composition of pulmonary surf actant at various stages of bleomycin induced lung injury. The signifi cance of these changes are not fully understood; however, the possibil ity exists that an abnormal surfactant results which in turn affects l ung function.