Abstract: OBJECTIVE To evaluate the in vivo pharmacodynamic of a specific antagonist of angiotensin II type 1 receptor(AT₁R) named hit 1(caffeic acid derivatives). METHODS The rat’s hypertension model by a two-kidney two clip(2k2c) method was performed. The rats were divided into 6 groups including sham group, model group, valsartan group (8.3 mg·kg^-1), hit 1 low, middle and high dose group(5, 15, 30 mg·kg^-1). These groups were orally administered at 8:00 once a day for 4 weeks. The in vivo pharmacodynamics of hit 1 was evaluated from 5 aspects including body weight, blood pressure, heart rate, cardiac mass index and histomorphology. And the effect of hit 1 on the expression of AT₁R in rat femoral artery was determined by Western blotting. RESULTS The mean systolic and diastolic blood pressure values of the rats after the 2k2c operation were (153.87±7.03)mmHg and (116.50±8.68)mmHg, indicating that the model of renovascular hypertensive rats was established successfully. Compared with the model group, hit 1 medium and high dose groups had the same effect as valsartan group, and could significantly reduce the blood pressure of renovascular hypertensive rats in a dose-dependent manner, without affecting their heart rate. However, the blood pressure of low dose hit 1 group was not significantly improved. Histomorphological studies showed that hit 1 could improve cardiac hypertrophy induced by hypertension in rats and reduce cardiac weight index. Moreover, hit 1 could also enhance the compliance and resistance of the femoral artery wall in renovascular hypertensive rats by significantly reducing the ratio of membrane area to cavity area. The result of Western blotting showed that hit 1 could significantly decrease the expression of AT₁R in rat femoral arteries.CONCLUSION This work provide potential possibilities for further evaluation of hit 1 which have significant antihypertensive activity in rats.