In the present study we investigated the protective role of endogenous glutathione, a known free radical scavenger, in rats subjected to carrageenan-induced pleurisy. In vivo depletion of endogenous glutathione pools with l-buthionine-(S,R)-sulfoximine (BSO, 1 g/kg for 24 h, intraperitoneally) enhances the carrageenan-induced degree of pleural exudation and polymorphonuclear leukocyte migration in rats subjected to carrageenan-induced pleurisy. Lung myeloperoxidase activity and lipid peroxidation were significantly increased in BSO pretreated rats. However, the inducible nitric oxide (NO) synthase in lung samples was unaffected by BSO pretreatment. Immunohistochemical analysis for nitrotyrosine revealed a positive staining in lungs from carrageenan-treated rats, which was massively enhanced by BSO pretreatment. Furthermore, in vivo BSO pretreatment significantly increased peroxynitrite formation as measured by the oxidation of the fluorescent dye dihydrorhodamine 123, enhanced the appearance of DNA damage, the decrease in mitochondrial respiration and partially decreased the cellular level of NAD+ in ex vivo macrophages harvested from the pleural cavity of rats subjected to carrageenan-induced pleurisy. In vivo treatment with exogenous glutathione (50 mg/kg i.p.) significantly reverts the effects of BSO and exerts anti-inflammatory effects. Thus, endogenous glutathione plays an important protective role against carrageenan-induced local inflammation.