Objective:To determine the effect of antiparallel phosphorothioate triplex-forming oligonucleotide(apsTFO),which was designed according to shear stress response element(SSRE) in tissue factor(TF) gene promoter region,on the expression of endothelial TF in carotid artery stenosis rats.Methods:Rat model of severe carotid artery stenosis were inflicted by silica gel tube ligation.Half an hour before the model infliction,GT20-apsTFO,GT20-psTFO and GT21-apsTFO labeled with green fluorescence(FITC) were injected into the vena caudalis of rat at a dose of 0.5 mg/kg.Half an hour,4 or 9 h after the ligation,the distribution of TFO in the common carotid artery,the liver and the kidney was detected with aid of fluorescence microscopy.And the mRNA and protein expressions of TF,Egr-1 and Sp1 in the above-mentioned organs were determined with in situ hybridization and immunohistochemical assay respectively in 6 h after the model establishment,and the results were analyzed with an image analysis system.Results:Only in 1 h after TFO injection,fluorescent granules appeared in the liver,the kidney and the vascular wall and lumen of carotid artery,and then in 4.5 h,they still deposited in above sites except the vascular lumen.GT20-apsTFO and GT21-apsTFO significant down-regulated the mRNA and protein expressions of TF compared to the rats without treatment(P<0.05),and the former apsTFO had a more stronger effect than the later(P<0.05).GT20-psTFO had no such effect(P>0.05).The 3 TFOs had no inhibition on the mRNA and protein expressions of Egr-1 and Sp1.Conclusion:Pretreated apsTFO can partly come into the vascular endothelial cells,and inhibit TF expression induced by shear stress,but had no effect on Egr-1 and Sp1 gene expressions. Objective: To determine the effect of antiparallel phosphorothioate triplex-forming oligonucleotide (apsTFO), which was designed according to shear stress response element (SSRE) in tissue factor (TF) gene promoter region, on the expression of endothelial TF in carotid artery stenosis rats . Methods: Rat model of severe carotid artery stenosis were inflicted by silica gel tube ligation. Half an hour before the model infliction, GT20-apsTFO, GT20-psTFO and GT21-apsTFO labeled with green fluorescence (FITC) were injected into the vena caudalis of rat at a dose of 0.5 mg / kg. Half an hour, 4 or 9 h after the ligation, the distribution of TFO in the common carotid artery, the liver and the kidney was detected with aid of fluorescence microscopy. And the mRNA and protein expressions of TF, Egr-1 and Sp1 in the above-mentioned organs were determined with in situ hybridization and immunohistochemical assay respectively in 6 h after the model establishment, and the results were analyzed with an image analysis syst em.Results: Only in 1 h after TFO injection, fluorescent particles appeared in the liver, the kidney and the vascular wall and lumen of carotid artery, and then in 4.5 h, they still deposited in above sites except the vascular lumen. GT20- apsTFO and GT21-apsTFO significant down-regulated the mRNA and protein expressions of TF compared to the rats without treatment (P <0.05), and the former apsTFO had a more stronger effect than the later (P <0.05) .GT20-psTFO had The 3 TFOs had no inhibition on the mRNA and protein expressions of Egr-1 and Sp1.Conclusion: Pretreated apsTFO can not come into the vascular endothelial cells, and inhibit TF expression induced by shear stress, but had no effect on Egr-1 and Sp1 gene expressions.