Abstract: Aim To investigate estradiol inhibition of neointimal prolife ration after rat carotid artery balloon injury.Methods Eight to ten-week old SD rats (male, n=21, female, n=21) were divided into intact control(n=7), gonadecto my control(n=7)and estradiol (n=7, gonadectomy) groups in each sex.Left carotid artery was not injured with 2.0 F PTCA balloon until estradiol was injected fo r three day s.Rats were killed 2 w k after injury. Neointimal areas and media area, ratio s of intimal areas/media areas were measured with computer.Results M ale neointimal areas and ratios of intimal areas /media areas in estradiol grouPwere less than those in intact control g rouPsignificantly(all P<0.01) and than those in gonadectomy control grouP(all P<0.05).T ho se in female, in estrdiol g rouPwere less than those in gonadectomy control grouPevidently (all P<0.01), and similar to those in intact control grouP(all P>0.05).Conclusion sEstrdiol inhibits neointimal proliferation after the gonadectomy in rats undergoing carotid artery balloon injury.

Key words: estradiol, neointimal prolife ration, smooth muscle cells, vascular endothelial injury, carotid