Aim To investigate the effect of rosiglitazone on the blood levels of nitric oxide(NO)and endothelin-1(ET-1) in insulin resistant rats and the underlying mechanism.Methods Male Sprague-Dawley(SD) rats were fed with high fructose to induce insulin resistant rats model,rats were treated with or without rosiglitazone after 4 weeks.At the end of 8th week,systolic blood pressure(SBP),fasting blood sugar(FBS),fasting serum insulin(FSI),blood lipids,NO,ET-1 and aortic nitric oxide synthase(NOS) activity were measured respectively in groups.Results Compared with control group,SBP,FSI and ET-1 in model group significantly increased;aortic NOS activity and NO levels were significantly lowered.At the same time,the abnormity of lipid metabolism appeared in the model group.After rosiglitazone treatment,SBP,FSI and ET-1 remarkably reduced;aortic NOS activity and NO levels significantly increased;insulin resistance and the abnormity of lipid metabolism were improved.While all indexes did not change significantly after rosiglitazone treated control rats.Conclusions Rosiglitazone may improve vascular endothelial function in rats with insulin resistance by decreasing blood pressure,increasing insulin sensitivity,improving the abnormity of lipid metabolism,besides,it could be associated with nitric oxide elevating by increasing nitric oxide synthase activity and inhibiting endothelin increasing.