Effect of astragaloside IV on relaxation and molecule mechanism in isolated rat aortic rings from hypertensive rats

AIM To investigate the effects of long-term treatment with astragaloside(As)Ⅳon blood pressure and vascular relaxation dysfunction in hypertensive model induced by aortic banding from adult rats. METHODS Hypertensive rat model was induced by aortic banding.Twelve weeks after surgery,the rats with or without aortic banding were randomized into six groups:sham,sham + AsⅣ3.3 mg·kg~(-1),model,model + AsⅣ0.33 mg·kg~(-1),model + AsⅣ1.0 mg·kg~(-1),model + AsⅣ3.3 mg·kg~(-1).Blood pressure was measured by the modified tail-cuff method once every four weeks.At the end of the 12-week treatment period,heart mass index (HMI) and left ventrical mass index(LVMI) were measured.Vascular hypertrophy was assessed by determination of standardized aortic weight.The relaxation effect of AsⅣon thoracic aortic rings isolated from hypertensive rats induced by aortic banding was recorded.Plasma and aortic nitrite/nitrate levels were determined by ELISA,and protein expression of eNOS was determined by western blotting.RESULTS The increasing systolic blood pressure of the rats with aortic banding was significantly reduced by AsⅣat the dose of 1.0 and 3.3 mg·kg~(-1),respectively.LVMI,HMI and standardized aortic weight were increased in the rats with aortic banding,and were attenuated by treatment with 3.3 mg·kg~(-1) AsⅣ.In the hypertensive rats,endothelium -dependent relaxation to ACh were markedly blunted as compared with sham-operated rats,and were improved by the administration of AsⅣwith concentration dependent.Moreover,aortic nitrite/nitrate and eNOS protein levels were reduced in the hypertensive rats.AsⅣattenuated the reduction of aortic nitrite/nitrate and eNOS protein levels.CONCLUSIONS Long-term treatment with AsⅣcould reduce blood pressure,regress vascular hypertrophy,and attenuate endothelial dysfunction in the aortic-banding rats,which is partly resulted from up-regulating protein expression of aortic eNOS and elevating nitrite/nitrate level.