Aim To investigate the expression of urotensin Ⅱ(UⅡ) and its receptor(UT) in the aorta and myocardium in a rat model of vascular calcification,and explore the significance of UⅡ system in vascular calcification. Methods Arterial calcification of Sprague-Dawley rats was induced by Vitamin D3 plus nicotine(VDN).Calcification was confirmed by Von Kossa staining and measurement of calcium content.Alkaline phosphatases(ALP) activity was also evaluated.UⅡ contents of plasma,aorta and myocardium were determined by radioimmunoassay,UⅡ immunoactivity and UT mRNA expression were determined by immunohistochemistry and RT-PCR,respectively. Results There were mass black granules deposited in aortic wall of the vascular calcified rats induced by VDN,with Von Kossa staining.Calcium content and ALP activity in calcified aorta of these rats were increased significantly than the control rats(P><0.01).Meanwhile,aortic UⅡ and UT mRNA levels in calcified rats,as well as myocardial UT mRNA level,were upregulated significantly compared with the control group.In addition,high arginine diet could reduce the degree of vascular calcification by Von Kossa staining.Calcium contents,UⅡ contents,and UT mRNA levels were slightly lower,but not significantly in the VDN plus arginine rats than in the VDN treated rats.Furthermore,VDN plus high methionine diet treatment could exacerbate vascular calcification.Aortic calcium contents,as well as aortic and myocardial UⅡ contents and UT mRNA expression,were further increased,while aortic ALP activity was decreased in the VDN plus methionine rats than in the calcified rats induced by VDN.There were no significant differences in plasma UⅡ contents among these groups. Conclusion This study found that UⅡ/UT system was significantly increased in calcified vessels,suggesting that UⅡ may be involved in the development of vascular calcification,in a paracrine and/or autocrine manner.