Effects of free fatty acid infusion on rabbit pulmonary surfactant. Influence of corticosteroids.

We studied the effect of free fatty acids (FFA) i.v. on alveolar lung surfactant content of rabbits. A FFA mixture was given in doses from 0.1 to 20 mg X kg-1 X min-1 during 15 min in seven different experimental series (n = 45). Disaturated phosphatidylcholine (DSPC) content in lung airway lavage fluid was measured as an index of alveolar surfactant pool. DSPC was significantly increased (p less than 0.05) by 86% in the series receiving 20 mg FFA X kg-1 X min-1 as compared to control values (means +/- SD: 4.4 +/- 1.1 mg DSPC X kg-1 body weight). Smaller doses of FFA did not change DSPC, but induced a dose-related pulmonary oedema. All the rabbits receiving 20 mg FFA X kg-1 X min-1 died before completion of the 15 min infusion; they were hypoxaemic, hyperventilated and had a decrease in lung compliance. Hydrocortisone (20 mg X kg-1 i.v.) and methylprednisolone (30 mg X kg-1 i.v.) administered 2 h before FFA blocked the increase of DSPC induced by 20 mg FFA X kg-1 X min-1. Both drugs decreased pulmonary oedema and tended to normalize some of the pulmonary function indices, although they did not modify the lethality. In conclusion, acute i.v. infusion of FFA increased alveolar surfactant pool and produced pulmonary oedema; pretreatment with corticosteroids reduced these effects and protected the lung from some of the noxious effects of FFA.