Contribution of blood pressure variability to the effect of nitrendipine on end-organ damage in spontaneously hypertensive rats

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Abstract
Objective It has been proposed that blood pressure variability (BPV) is positively related to end-organ damage (EOD) in hypertension. The present work was designed to observe the effects of long-term treatment with nitrendipine and hydralazine on BPV and EOD in spontaneously hypertensive rats (SHR), to examine the hypothesis that lowering BPV with an antihypertensive drug is an important factor in organ protection. Design and methods Drugs were mixed in rat chow. After 4 months of drug administration, blood pressure was recorded continuously in conscious freely moving rats for 24 h. The heart, kidneys, and brain were then isolated and examined. Results It was found that nitrendipine significantly decreased blood pressure 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 = 0.331, P< 0.05) and closely related to long-term systolic BPV (r = 0.551, P< 0.01). In nitrendipine-treated rats, EOD score was closely related to long-term systolic BPV (r = 0.602, P< 0.01), but not to BP level (r = 0.174, P> 0.05). Conclusion BPV plays an important role in the organ-protecting effects of nitrendipine.