Aim To explore the function of angiotensin Ⅱ (AngⅡ) in promoting osteopontin gene expression and protein synthsis of rat vascular adventitial fibroblasts. Methods Cultured cells were incubated with 1 different concentration of AngⅡ for different hours and AngⅡ plus AT1 receptor blocker,losartan or/and AT2 receptor blocker,PD123319. Then RT-PCR and WesternBlotting analysis were used to observe the effect of AngⅡ on osteopontin gene expression of rat vascular adventitial fibroblasts. Results AngⅡ(10-6 mol/L)obviously enhanced the expression of OPN mRNA in adventitial fibroblasts in time-dependent manner, the ratio of mRNA of osteopontin and β-actin in cells incubated with AngⅡ for 6,12 and 24 h increased by 65.43%, 97.03% and 105.11% respectively,as compared with that of the control (P<0.05), whereas there was no significant change in negative control at 24 h. AngⅡ could induce gene expression of osteopontin in dose-dependent manner, cells incubated with 10-8, 10-7, 10-6 and 10-5 mol/L AngⅡ for 12 h, there was up-regulation of OPN mRNA expression by 70.46%, 97.37%, 123.10% and 147.59% respectively (P<0.01).Pre-treatment with losartan(10-5 mol/L) and/or PD123319(10 mmol/L) for 1h in adventitial fibroblasts before AngⅡ(10-6 mol/L) used,the expression of OPN mRNA was inhibited by 58.9%, 0.92% and 59.7% respectively . Westernblotting analysis also showed that protein synthesis of osteopontin in cells incubated with 10-8, 10-7, 10-6 and 10-5 mol/L AngⅡ for 12h increased by 50.68%, 63.03%, 69.86% respectively ,as compared with that of the control(P<0.05). Pre-treatment with losartan(10-5 mol/L) but not PD123319 (10 mmol/L) before AngⅡ (10-6 mol/L) used, could inhibited the expression of OPN protein. Conclusions AngⅡ may up-regulate osteopontin gene expression and protein synthesis of rat vascular adventitial fibroblasts via angiotensin type 1 receptor.