Effects of mannitol on the acute lung injury induced by oleic acid in rats

Our purpose was to evaluate the pulmonary effects of mannitol infusion in a rat model of acute lung injury induced by oleic acid (OA) to compare the e ffects of mannitol to those of another diuretic, furosemide (FUR), and to a ssess if mannitol effects remained after correction of the volume depletion induced by this agent. Acute lung injury was induced in Wistar rats by int ravenous administration of 100 mg/kg of OA. Mannitol (1 mL of a 20% solutio n) was infused either 15 min before or 2 h after OA infusion. FUR was infus ed intravenously in a dose (1 mg/kg) that induced a similar amount of diure sis compared to mannitol. We also studied rats that received NaCl 0.9% infu sion to correct for volume losses induced by mannitol. The severity of the acute lung injury was evaluated by morphometric studies of the lungs 4 h af ter OA infusion. The amount of intraalveolar fluid accumulation and the int ensity of alveolar distention and collapse were evaluated. Mannitol infusio n either 15 min before or 2 h after OA administration resulted in a signifi cant decrease in the amount of intraalveolar edema and alveolar distention and collapse (P < 0.001). FUR administration before OA infusion had an effe ct similar to mannitol. We did not observe any significant effect of mannit ol when the rats received saline infusion to correct for diuresis induced b y mannitol. We conclude that mannitol decreases the severity of pulmonary i njury induced by OA in rats. This effect is mainly due to its diuretic prop erties.