Abstract: Objective To study the effects of different ratios of polyunsaturated fatty acids(PUFA) on ulcerative colitis induced by dextran sulfate sodium(DSS) in rats.Methods Forty male rats were randomly divided into five groups:normal control group,model control group,three PUFA groups:(n-6/n-3=1:1,5:1,10:1).Ulcerative colitis model in rats was induced by dextran sulfate sodium.Rats were fed with ordinary diets in the normal group and model control group,while the remaining three groups received different ratios of PUFA.Stool consistency,diarrhea,and bloody stools of the rats were checked during the experiment.The colon sample was extracted,and the colon weight/length ratio(mg/cm) was assessed.The activities of myeloperoxidase(MPO),superoxide dismutase(SOD),and the contents of malonyldialdehyde(MDA) in serum were detected with biochemistry method.Interleukin-1 beta(IL-1β) interleukin-6(IL-6) and interleukin-10(IL-10) levels in serum were measured with enzyme-linked immunosorbent assay(ELISA) by the end of the experiment.Results Compared with the model control group,the colon weight/length ratio(79.90±13.84 mg/cm) and the content of MDA(3.52±0.65 nmol/mL) in n-6/n-3 ratio of 5:1 group were significantly lower(P<0.05) and the activity of SOD(245.69±15.49 U/mL) in serum was significantly higher(P<0.01 for all).Compared with n-6/n-3 of 1:1 and 10:1group,the content of IL-6(7.01±4.21 pg/mL) was significantly lower(P<0.01) and the content of IL-10(10.95±7.97pg/mL) was significantly higher(P<0.05) in n-6/n-3 ratio of 5:1 group.ConclusionIn this study,the n-6/n-3 ratio of 5:1 of PUFA has significant protective effects on ulcerative colitis induced by DSS in rats and the effects may be related to antioxidation and anti-inflammation.