Lipopolysaccharide (LPS) from gram-negative bacteria is a major factor that contributes to multiple organ failure including lung injury. Among LPS-induced metabolites, reactive oxygen species are considered to play a crucial pathogenic role in the lung damage. In this study, the effect of early administration of an antioxidant, alpha-lipoic acid (LA), on bronchoalveoar lavage fluid (BALF) lipid peroxidation, hydrogen peroxide (H(2)O(2)), sulphydryl group (-SH) concentration and total protein concentration was evaluated in rats with endotoxic shock induced by administration of LPS (Escherichia coli 026:B6, 30 mg/kg, i.v.). The animals were treated intravenously with normal saline or LA (60 mg/kg or 100 mg/kg i.v.) 30 min after LPS injection. Five hours after LPS or saline administration, the animals were sacrificed and BALF was obtained for measurements. The results showed that the levels of oxidative markers, thiobarbituric acid reactive substances (TBARS) and H(2)O(2) were increased significantly in BALF, whereas they were decreased significantly on treatment with LA. The concentrations of -SH groups were significantly increased and total protein concentration was insignificantly decreased in the LPS/LA group. There was no difference in oxidative stress reduction between 60 mg/kg and 100 mg/kg doses. These results indicate that early administration of lipoic acid provides protective effects against endotoxin-induced oxidative stress in the lung and supports the idea that alpha-lipoic acid is a free radical scavenger and a potent antioxidant.