Objective:To investigate the effect of melatonin(MLT) on airway oxidative stress in rats with chronic obstructive pulmonary disease(COPD).Methods:36 male wistar rats were randomly divided into 3 groups as follows:control group

COPD group and MLT group.The COPD model was established by intratracheal lipopolysaccharide(LPS) and exposure to cigarette smoking for 28 days

the MLT group was given intraperitoneal injection of 10 mg/kg MLT 30 minutes before each cigarette challenge.After incision of trachea

the lung function was measured.Then the rats were lavaged

the total and different white blood cell counts of bronchial alveolar lavage fluid(BALF) were determined;nitric oxide(NO)

malondialdehyde(MDA)

superoxide dismutase(T-SOD)

glutathione superoxide(GSH-PX) were carried out respectively.The pathological changes were observed under light microscope.Result :(1)Significant decrease in total white blood cells and neutrophils in BALF was found in MLT group than these in COPD group(P<0.01

P<0.05

respectively)

and the ratio of monocyt-macrophage was lower in MLT group.(2) NO and MDA in BALF of MLT group significantly decreased(P<0.05)

while T-SOD and GSH-PX in BALF of MLT group significantly increased(P<0.05)

as compared with those of COPD group.(3) Forced expiratory volume in 0.3 second(FEV0.3)

forced expiratory volume in 0.3 second /forced vital capacity(FEV0.3/FVC) and peak expiratory flow(PEF) in MLT group were higher than those in COPD group

but there were no obvious differences between these groups.(4) The model rats shared specific pathological features in bronchial walls and lung tissues

and the pathological damages in MLT group were lessened but still abnormal.Conclusion:Early intervention with MLT can partly inhibit proceeding of COPD by decreasing airway oxidative stress and increasing activity of antioxidant.