Objective To investigate the process of intimal thickening and the effect of losartan, an antagonist of
angiotensin Ⅱ AT
1 receptor,on it.\ Methods\ Models of aortic endothelial denudation of rats by balloon catheter were made. The rats were randomly allocated into three groups: group 1( n =24) served as a control, group 2( n =24) were given vascular balloon injury, group 3( n =24) were given losartan(30mg/kg·d -1 ) from 1 day before injury to 28 days after injury. The aortic tissues were taken at day 3,7,14 and 28 . The process of intimal thickening and the effect of losartan on it were investigated histologically.\ Results \ The migration and
proliferation of vascular smooth muscle cells(VSMC) existed at day 3 after balloon injury. The intimal thickening began at day 7 after injury. The proliferation of VSMC was more significant at day 14. The proliferation of VSMC decreased obviously at day 28,but extracellular matrix increased and the intimal thickening continued. When given losartan, the proliferation of VSMC and the intimal thickening decreased.\ Conclusion\ Losartan can inhibit the migration and proliferation of vascular smooth muscle cells led by endothelial injury and reduce the extent of intimal thickening. <