NEW YORK (Reuters Health) - In patients with renovascular hypertension, excessive oxidative stress appears to contribute to impaired endothelium-dependent vasodilation, Japanese researchers report.

Writing in the June 20th issue of The New England Journal of Medicine, Dr. Yukihito Higashi and colleagues from Hiroshima University report on 15 patients who had renovascular hypertension, and on 15 age- and sex-matched normotensive controls.

The researchers measured the response of forearm blood flow to infusions of acetylcholine, an endothelium-dependent vasodilator, and to isosorbide dinitrate, an endothelium-independent vasodilator. In the case of the 15 renovascular hypertension patients forearm blood flow was measured before and after renal-artery angioplasty.

At baseline, blood flow in both groups of patients responded similarly to isosorbide dinitrate. However, there was less response to acetylcholine in the patients who had renovascular hypertension, compared with normotensive controls (p<0.001), Dr. Higashi's team found.

Renal artery angioplasty in the renovascular hypertensive patients resulted in decreases in systolic and diastolic blood pressure, forearm vascular resistance and urinary excretion of 8-hydroxy-2'-deoxyguanosine and serum malondialdehyde-modified LDL, which are indicators of oxidative stress.

Also, angioplasty increased the forearm blood flow in response to acetylcholine, and this increase correlated with the decreases in urinary excretion of 8-hydroxy-2'-deoxyguanosine and in serum malondialdehyde-modified LDL.

Infusions of ascorbic acid improved the response of forearm blood flow during acetylcholine infusion before angioplasty, but not after renal artery angioplasty, the investigators add.

Dr. James R. Sowers, from the State University of New York Downstate Medical Center in Brooklyn, comments in an editorial: "Some of the improvement in endothelial function and associated reductions in oxidative stress after angioplasty may have been due to reductions in blood pressure, even though the changes were not statistically correlated."

N Engl J Med 2002;346:1954-1962,1999-2001.

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