Oleic acid inhibits alveolar fluid reabsorption -: A role in acute respiratory distress syndrome?

Levels of oleic acid (OA) are elevated in plasma and bronchoalveolar lavage fluids of patients with acute respiratory distress syndrome (ARDS). CIA is also widely used. to provoke edema, by unknown mechanisms, in experimental models of ARDS. We investigated the impact of intravascularly applied CIA on epithelial lining fluid balance. OA (25 muM) dramatically blocked active transepithelial Na-22(+) transport (by 92%) in an isolated, ventilated, and perfused rabbit lung model, provoking alveolar edema, assessed by increases in lung weight and epithelial lining fluid volume. OA did not alter epithelial permeability, measured by [H-3]mannitol and fluorescently labeled albumin flux, but did increase endothelial permeability, assessed by capillary filtration coefficient. In A549 cells, OA completely blocked amiloride-sensitive sodium currents measured by patch clamp, and also largely abrogated ouabain-sensitive Na+,K+-ATPase-mediated Rb-86(+) uptake. Although OA did not alter epithelial sodium channel or Na+,K+ -ATPase surface expression, it covalently associated with both molecules and directly, dramatically, and dose-dependently inhibited the catalytic activity of purified Na+,K+ -ATPase. Therefore, CIA impaired the two essential transepithelial active sodium transport mechanisms of the lung, and could thus promote alveolar edema formation and prevent edema resolution, thereby contributing to the development of ARDS.