[Anti-oxidantive effect of methylene blue on acute lung injury induced by paraquat in rat].

OBJECTIVE: To study the protection effects of methylene blue on acute lung injury that induced by paraquat in rats. METHODS: 24 male SD rats were randomly distributed into four groups of 6 rats each group including control group, methylene blue group, paraquat group and paraquat plus methylene blue group. The rats were challenged acutely with paraquat( 25 mg/kg, i. p. ). After two hours treatment, the rats in paraquat plus methylene group were treated by methylene blue( 2 mg/kg, i. p. ) or vehicle treatment for 24 hours. Then, lung specimens were collected for pathological examinations and biochemical analysis including content of malondialdehyde( MDA) and activity of lactate dehydrogenase( LDH) and superoxide dismutase( SOD). The bronchoalveolar lavage fluids were also collected for the analysis of myeloperoxidase( MPO) activity. RESULTS: Compared to control group, the rats treated with paraquat induced acute lunginjury which was reflected by the increase of pathological score( P < 0. 05) and wet/dry ratio of lung tissue( P < 0. 05). Moreover, the content of MDA and LDH were increased, but the activity of SOD was decreased in lung tissues, and the activity of MPO were increased in bronchoalveolar lavage fluid in rats treated with paraquat. Compared to the rats with paraquat exposure, the pathological score( P < 0. 05) and wet/dry ratio( P <0. 05) in the rats treated with paraquat plus methylene blue were decreased. The content of MDA( P < 0. 05) and LDH( P < 0. 05) were also decreased, but the activity of SOD was increased( P < 0. 05). Moreover, the activity of MPO in bronchoalveolar lavage fluid was decreased in paraquat exposure rats with methylene blue treatment. CONCLUSION: Acute lung injury that induced by paraquat in rats is protected by methylene blue. The result may provide a new way to treat patients with acute paraquat poisoning.