Abstract: AIM: To evaluate the effects of valsartan on the structure and function of vessels in spontaneously hypertensive rats(SHR).METHODS: 30 twelve-weekold male SHRs were divided into three groups at random:untreated control(n=10),low-dose valsartan(10mg·kg^-1·d^-1,n=10),and high-dose Valsartan(30mg·kg^-1·d^-1,n=10).Valsartan was given by gavage for 4 weeks,while SHR control and 10 age- and sexmatchedWistar Kyoto rats(WKY)were given water only.Systolic bloodPressure(SBP)was measured using tailcuff technique.Wall tolumen area ratios(Wl)of thoracic aorta and mesenteric artery(3rd grade branch)were assessed by morphormetic assay.The effect of valsartan on the vascular reactivity o the vasoactive substance:norepinephrine and sodium nitroprusside were studied by using rings of thoracic aorta and mesenteric arteries isolated from rats.RESULTS: After 4-week treatment,thelevels of SBPin both high andlow-dose groups were significantlylower than those in control grouP(P<0.05).The values of Wl of mesenteric artery in the two treatment groups were markedly reduced than those in the control grouP(P<0.05),and the values of Wl of thoracic aorta in the high -dose grouPwere markedly reduced than those in the control grouP(P<0.01).Both mesenteric artery and thoracic aorta in valsartan treated groups exhibited significantly depressed function of vasoconstriction response to noradrenaline and enhanced function of vasodilation to SNP.CONCLUSION: Valsartan can meliorate the function of resistant vessels by enhancing their sensitivity to vasodilator and depressing the sensitivity to vasoconstrictor;and also attenuate the resistant vascular hypertrophy during the development of hypertension in SHR.

Key words: pharmacodynamics, spontaneously hypertensive rats, valsartan, vasoconstriction, vasodilation, hypertension