INHIBITION BY METHYLPREDNISOLONE OF LEUKOCYTE-INDUCED PULMONARY DAMAGE

Background and Methods: The purpose of this study was twofold: the development of a chronic model of leukocyte-mediated pulmonary injury and the evaluation of the protective effects of methylprednisolone. Rabbits were inoculated ip with zymosan. Blood gases and circulating leukocytes were evaluated. Survivors were killed on day 10 for microscopic studies and for the evaluation of lung lipid peroxidation through the by-product malondialdehyde. Results: Intraperitoneal zymosan resulted in a marked decrease of PaO2 and circulating leukocytes, and increased cellularity of alveolar septa, interstitial edema, and increased lung malondialdehyde. Pulmonary damage was partially prevented when methylprednisolone was administered before zymosan inoculation, but not when methylprednisolone was given 24 hr later. Conclusions: The authors conclude that a local nonseptic inflammatory stimulus may provoke remote changes to the lungs and that methylprednisolone may counteract the process only if it is administered before or very early after the onset of inflammation.