[The effect of aminoguanidine, a nitric oxide synthase inhibitor, on bleomycin-induced lung injury in rats].

To observe the dynamic change of the nitric oxide synthase (NOS) activity of the lung in bleomycin -induced pulmonary fibrosis in rats and to investigate the effect of aminoguanidine (AG), a selective inhibitor of inducible NOS on this animal model. Sixty SD rats were divided into three groups in random: control group, untreated model group, AG-treated group. On experimental day (day 0), the rats were intratracheally instilled with bleomycin (5 mg/kg body weight) or sterile saline, and then treated with AG (50 mg x kg(-1)) x d(-1)), intraperitoneally) or saline until they were killed. On days 3, 7, 14, 28 after instillation, five rats of each group were sacrificed and the lungs were harvested for histopathological examination and determination of NOS activity, MDA and TNF. NOS activity in the lung homogenate was elevated quickly after bleomycin instillation and peaked on day 7, then declined. Treatment of AG remarkably ameliorated the alveolitis caused by bleomycin. The subsequently pulmonary fibrosis was also decreased, but there was no statistically significance. AG did not affect the increased level of MDA and TNF-alpha caused by intratracheally instilled bleomycin. Nitric oxide seems to play an important role in the development of pulmonary fibrosis, especially in the alveolitis phase.