AIM:To observe the protective effects of tea polyphenols (TP) on injury of lung induced by intestinal ischemia reperfusion (I/R) in rats, and comprehend whether this action is on dose-dependent manner. METHODS: The experiment was conducted in the Staff Room of Pharmacology, Dalian Medical University from March to July 2004. ① 60 male SD rats were randomized into sham-operation group, model group and 100.0, 50.0, 25.0, 12.5 mg·kg-1 TP group. ② Rats in each TP group received ranine vein injection of TP of corresponding dose, and rats in the model group and sham-operation group were administrated with normal saline of the same volume; The intestinal I/R injured model was established by reperfusing for 120 minutes following 20-minute clamping of superior mesenteric artery; Rats in the sham-operation group received no clamping of superior mesenteric artery. ③ After 120-minute reperfusion, blood and lung samples were got in all groups. The concentration of superoxide dismutase (SD), malonaldehyde (MDA) and nitrogen oxide (NO) in serum and lung samples as well as protein content in lung perfusate were determined. Morphological changes of lung were observed under light microscope. RESULTS: A total of 60 rats entered the final analysis. ① Compared with model group, SD activity in serum of rats in the 12.5,25.0,50.0 and 100.0 mg/kg TP group increased 38.55%,125.37%,181.58%and 185.34%(P < 0.05,0.01) respectively, the concentration of MDA decreased 55.83%,63.
56%,74.20% and 80.61% (P < 0.01) respectively, the concentration of NO decreased 11.66%,31.97%,43.24% and 84.78% (P < 0.05,0.01) respectively. ② In comparison with the model group, SOD activity of rats in the 12.5,25.0,50.0 and 100.0 mg/kg TP group increased 8.12%(P > 0.05),116.89%,186.24% and 233.59% (P < 0.01) respectively, the content of MDA decreased 34.54%(P > 0.05),72.69%,75.10% and 80.72%(P < 0.01) respectively, the concentration of NO decreased 30.25%,54.61%,92.87% and 92.67% (P < 0.01) respectively. ③ Compared with the model group, protein content in lung perfusate of rats in the 12.5,25.0,50.0 and 100.0 mg/kg TP group decreased 55.98%,70.57%,75.03% and 82.00% (P < 0.01) respectively. ④ Test with microscope indicated that there were significant morphological injuries in lungs of the model group, and compared with the model group, the reduction of lung changes in each TP group were in dose-dependent manner. CONCLUSION: TP has a dose-dependent protective effect on lung injury induced by intestinal I/R, this may relate to its free radical eliminating action, the diminishing of heterophil granulocyte aggregation and activation as well as the inhibition of great releasing of NO.