Objective:It has been proposed that blood pressure variability(BPV ) is positively related to end- organ dam - age(EOD) in hypertension.The presentwork was designed to observe the effects of long- term treatm ent with nitrendipine and hydralazine on BPV and EOD in spontaneously hypertensive rats(SHR) ,to exam ine the hypothesis thatlowering BPV with an antihypertensive drug is an im portant factor in organ protection.Design and methods:Drugs were m ixed in rat chow .After 4 months of drug adm inistration,blood pressure was recorded continuously in conscious freely moving rats for 2 4 h.The heart, kidneys,and brain were then isolated and exam ined.Results:It was found that nitrendipine significantly decreased blood pres- sure and BPV ,and significantly decreased EOD score in SHR.Hydralazine decreased blood pressure,but did not lower BPV. No effect on EOD was found in hydralazine- treated rats.In control rat(n=38) ,EOD score was weakly related to systolic blood pressure(r=0 .331 ,P<0 .0 5 ) and closely related to long- term systolic BPV(r=0 .5 5 1 ,P<0 .0 1 ) .In nitrendipine- treat- ed rats,EOD score was closely related to long- term systolic BPV (r=0 .6 0 2 ,P <0 .0 1 ) ,but not to blood pressure level (r=0 .1 74 ,P>0 .0 5 ) .Conclusion:BPV plays an important role in the organ- protecting effects of nitrendipine. Objective: It has been proposed that blood pressure variability (BPV) is positively related to end-organ dam-age (EOD) in hypertension. The present work was designed to observe the effects of long- term treatm ent with nitrendipine and hydralazine on BPV and EOD in spontaneously hypertensive rats (SHR), to exam ine the hypothesis that low BPV with an antihypertensive drug is an im portant factor in organ protection. Design and methods: Drugs were m ixed in rat chow. After 4 months of drug admistration, blood pressure was recorded continuously in conscious freely moving rats for 2 4 h. The heart, kidneys, and brain were then isolated and examined. Results: It was found that nitrendipine significantly decreased blood pres- sure and BPV, and significantly decreased EOD score in SHR.Hydralazine decreased blood pressure, but did not lower BPV. No effect on EOD was found in hydralazine-treated rats. In control rats (n = 38), EOD score was weakly related to systolic blood pressure (r = , P <0. 05) and closely related to long-term systolic BPV (r = 0 .5 5 1, P <0 01) .In nitrendipine-treat- ed rats, the EOD score was closely related to long- term systolic BPV (r = 0.602, P <0.01), but not to blood pressure level (r = 0.114, P> 0.05) .Conclusion: BPV plays an important role in the organ- protecting effects of nitrendipine.