Serum ferritin levels are increased in subjects at-risk for or with acute lung injury (ALI), and there are observations to suggest that increases in serum ferritin levels may help predict the development of ALI in at-risk individuals. To deepen our understanding of increases of serum ferritin and their relationship to the development of ALI, we measured serum ferritin levels before and after intestinal ischemia/reperfusion (I/R) injury in rats, and found that serum ferritin levels increased significantly following I/R. Increases in serum and lavage ferritin levels paralleled increases in lung inflammation (lavage leukocyte numbers and tissue myeloperoxidase activities) and lung leak (lavage protein levels). In contrast, pre-treatment of rats with mepacrine (60 mg/kg, i.p.), a phospholipase A2 inhibitor, attenuated not only I/R-induced serum and lavage ferritin increases, but also the development of ALI. These findings indicate that, besides of human subjects with ALI, serum ferritin levels increase early on also in an animal model of ALI. Therefore, serum and lavage ferritin can be a candidate for early biomarker of ALI.