A Possible Modulatory Role of Nitric Oxide in Paraquat-induced Lung Injury in Mice

Abstract

The present study was undertaken to evaluate whether stimulation or inhibition of Nitric Oxide (NO) synthesis could affect lung toxicity induced by acute administration of paraquat (PQ) in mice. L-arginine (L-arg.), NG-nitro-L-arginine methyl ester (L-NAME) and aminoguanidine (AG) were employed as NO precursor, competitive and specific NO synthesis inhibitors, respectively. PQ was administered intraperitoneally to Swiss albino mice at a single dose of 50 mg kg -1 . L-arg. (700 mg kg -1 day-1), L-NAME (150 mg kg -1 day -1 ) or AG (100 mg kg -1 day -1 ) was given in drinking water of mice for 5 days before and one day after PQ administration. Appropriate controls were performed. PQ administratio n resulted in a pronounced elevation in lipid peroxides (157%) as well as decreased activity of alkaline phosphatase (ALP) (48%) and non-protein thiols (40%) in lung tissue compared to control non-treated mice as evidences of lung injury. Serum level of NO end products, nitrate and nitrite significantly elevated due to PQ administration (150%) as compared to control level. In mice given combined treatment of L-arg. and PQ, a remarkable rise in the serum level of nitrate and nitrite (140%) compared to the PQ group was observed. In addition, L-arg. ameliorated the increased level of lipid peroxides and non-protein thiols depletion as well as the decreased activity of ALP caused by PQ respectively. On the other hand, L-NAME and AG potentiated the deleterious effects of PQ on serum NO, lung lipid peroxides content, non-protein thiols content and alkaline phosphatase activity. In conclusion, PQ-induced lung injury in mice is alleviated by L-arg. but exacerbated by L-NAME and AG supplementati on. This could point out to a possible protective role of NO in PQ lung toxicity.