Objective:To investigate the action mechanism of Dihuang Yinzi on hypertension progress of spontaneously hypertensive rats（SHR）

and understand the role of endothelial function recovery by Dihuang Yinzi.Method:Fifty-four male SHR were divided into three groups:the control;Dihuang Yinzi treatment;and captoril treatment.Dihuang Yinzi（crude drug 15.9 g.kg-1.d-1） and captoril（3.375 g.kg-1.d-1） were treated from wk 7 to wk 24（wk = week） through gavage.The drug effect was observed at wk 18 and wk 24 during the treatments and 8 wk（wk32） after treatment.Experiments including the blood pressure by arterial carotis cannula;the concentration of NO 2-by Griess;the Ach-dependent relaxation of mesenteric rings by isometric tension change;and the mRNA expressions of IL-1

IL-6

TNF-α and iNOS of aorta tissue by real time PCR.Result:Dihuang Yinzisignificantly reduced blood pressure at wk18

and increased Ach-dependent relaxation of mesenteric rings and the NO 2-concentration in serum at wk18 and wk24.The mRNA expression of IL-1

IL-6

TNF-α and iNOS was markedly inhibited by the herb formula.Although captopril showed stronger anti-hypertensive effect

which could not extended after drug withdraw.In addition

the beta blocker did not enhance Ach-dependent vasodilation.NO 2-levels in serum and IL-1

IL-6 expression of aorta tissue were increased by captopril

while iNOS and TNF-α were inhibited at wk 24.Conclusion:Dihuang Yinzi showed anti-hypertensive effect with enhanced endothelium-dependent vasodilation in mesenteric artery and increased NO 2-concentration in serum.Furthermore

the herb formula also exerted anti-inflammatory effect by decreasing IL-1

IL-6

TNF-α and iNOS expression.