Background Repeated attacks of bronchial asthma lead to different degrees of airway remodeling,the mechanism of which is not yet clear. Some evidences indicate that it is related to the excessive expression of some growth promotion factors. Angiotensin Ⅱ is a polypeptide that may be involved in airway remodeling. To evaluate its role in airway remodeling in asthma,we observed the effects of an angiotensin Ⅱ type 1 receptor antagonist (valsartan) on the expression of collagen Ⅲ,collagen Ⅴ,and transforming growth factor β_1 (TGF-β_1) mRNA and protein in the airway walls of sensitized rats.Methods Forty Wistar rats were randomly divided into 5 groups: control group,sensitized group,and valsartan groups 1,2,and 3. The rats in the sensitized group and in valsartan groups 1,2,and 3 were sensitized and challenged with ovalbumin. Rats in control group were sensitized and challenged with 0.9% NaCl. Rats from valsartan groups 1,2,and 3 were drenched with valsartan (10 μg, 20 μg,or 30 μg,respectively) at the time of the ovalbumin challenges. The expression of collagen Ⅲ,collagen Ⅴ,and TGF-β_1 protein were detected using immunohistochemical method in combination with image analysis methods. The expression of TGF-β_1 mRNA was detected by in situ hybridization. Results The expression in the airways of collagen Ⅲ and collagen Ⅴ was significantly higher in rats from the sensitized group (7.73±0.81, 1.34±0.28) and from valsartan groups 1,2,and 3 (5.73±0.64, 1.13±0.15; 4.96±0.51, 0.98±0.08; 4.43±0.35, 0.93±0.06,respectively) than those in the control group (2.65±0.38, 0.67±0.08,P <0.05). In addition,collagen levels were significantly lower in valsartan groups 1,2,and 3 than those from the sensitized group ( P <0.05). The expression of TGF-β_1 mRNA and protein in the airways was significantly higher in rats from the sensitized group (20.49%±3.46%,29.73%±3.25%) and from valsartan groups 1,2,and 3 (16.47%±1.94%, 19.41%±1.87%; 14.38%±1.58%, 18.29%±1.43%; 12.96%±1.73%, 18.63%±1.11%,respectively) than that from the control group (7.84%±1.61%, 5.63%±1.07%,P <0.05). TGF-β_1 mRNA and protein levels were significantly lower in valsartan groups 1,2,and 3 than that in the sensitized group ( P <0.05). Conclusions Angiotensin Ⅱ receptor antagonist valsartan can suppress synthesis of collagen Ⅲ and collagen Ⅴ by downregulating TGF-β_1 mRNA and protein expression. Valsartan can decrease airway remodeling and could play a role in asthma therapy. Background Repeated attacks of bronchial asthma lead to different degrees of airway remodeling, the mechanism of which is not yet clear. Some evidences that that is not related to the excessive expression of some growth promotion factors. Angiotensin II is a polypeptide that may be involved in To evaluate its role in airway remodeling in asthma, we observed the effects of an angiotensin Ⅱ type 1 receptor antagonist (valsartan) on the expression of collagen Ⅲ, collagen Ⅴ, and transforming growth factor β_1 (TGF-β_1) mRNA and protein in the airway walls of sensitized rats. Methods Forty Wistar rats were divided into 5 groups: control group, sensitized group, and valsartan groups 1, 2, and 3. The rats in the sensitized group and in valsartan groups 1, and 3 were sensitized and challenged with ovalbumin. Rats in control group were sensitized and challenged with 0.9% NaCl. Rats from valsartan groups 1, 2, and 3 were drenched with valsartan (10 μg, 20 μg, or 30 μg, respectively) at the time of the ovalbumin challenges. The expression of collagen Ⅲ, collagen Ⅴ, and TGF-β_1 protein were detected using immunohistochemical method in combination with image analysis methods. The expression of TGF-β_1 mRNA was detected by in situ hybridization. Results The expression in the airways of collagen III and collagen Ⅴ was significantly higher in rats from the sensitized group (7.73 ± 0.81, 1.34 ± 0.28) and from valsartan groups 1, 2, and 3 (5.73 ± 0.64, 1.13 ± 0.15 ; 4.96 ± 0.51, 0.98 ± 0.08; 4.43 ± 0.35, 0.93 ± 0.06, respectively) than those in the control group (2.65 ± 0.38, 0.67 ± 0.08, P <0.05) 1, 2, and 3 than those from the sensitized group (P <0.05). The expression of TGF-β 1 mRNA and protein in the airways was significantly higher in rats from the sensitized group (20.49% ± 3.46%, 29.73% ± 3.25 %) and from valsartan groups 1, 2, and 3 (16.47% ± 1.94%, 19.41% ± 1.87%; 14.38% ± 1.58%, 18.29% ± 1.43%; 12.96% ± 1.73%, 18.63% ± 1.11%, resp(7.84% ± 1.61%, 5.63% ± 1.07%, P <0.05). TGF-β_1 mRNA and protein levels were significantly lower in valsartan groups 1, 2, and 3 than that in the sensitized group (P <0.05). Conclusions Angiotensin Ⅱ receptor antagonist valsartan can suppress synthesis of collagen Ⅲ and collagen Ⅴ by downregulating TGF-β_1 mRNA and protein expression. Valsartan can decrease airway remodeling and could play a role in asthma therapy.