Effect of Captopril and Losartan on the Blood Pressure of the Renovascular Hypertensive Rats

Objective: To study the therapeutic effect and characteristics of captopril and losartan Methods: (1)The isolated vascular ring was employed to assess the angiotension Ⅱ(AⅡ)-induced vascular contractility.(2)The renovascular hypertensive rat model of clipped one kidney was made and blood pressure was measured through carotid canula and tail-cuff manometer. Results:(1)Isolate vascular ring study:AⅡ induced a dose-dependent vasoconstriction response. The maximal effective dose captopril (0.1 mg/kg) showed a slight inhibitory actions to small doses of AⅡ and its inhibitory action was obviously weaked with increase of doses while losartan could completely block the AⅡ-induced vasoconstriction in the same condition.(2) Acute depressor effects:The maximal effective dose of captopril decreased the mean blood pressure(MAP) of rats from the control value of (18.37 ± 3.93)kPa to (8.70 ± 1.23)kPa, whereas losartan in the dose of 2 mg/kg(the maximal effective dosage) did not decrease the blood pressure again. While on the other hand, losartan was given at first in the other group, MAP decreased from (16.75 ± 1.14) kPa to (11.45 ± 2.45) kPa and blood pressure steadily decreased to (9.33 ± 1.77) kPa again after reapplication of the maximal dose of captopril. The two results had statistical difference(P 0.05). Conclusion: (1) Losartan can directly make effect by inhibiting AⅡ receptor, while isolated captopril can make effect by decreasing the product of endogenetic AⅡand the effect is weaker than that of the losartan. (2)The maximal effect of decreasing blood pressure by captopril is stronger than that of losartan in vivo.