Oxidative Stress Impairs Endothelial Function in Nondipper Hypertensive Patients

Aims: Essential hypertension, as well as other established cardiovascular risk factors, is associated with endothelial dysfunction. Hypertensive patients with a nondipper circadian pattern have a greater risk of cerebrovascular and cardiovascular complications in comparison with those with a dipper circadian pattern. In this study, we evaluated the association between nondipper pattern and endothelial function in patients with essential hypertension.

Methods: We evaluated the forearm blood flow (FBF) response to intraarterial acetylcholine (ACh), an endothelium-dependent vasodilator, and sodium nitroprusside (SNP), an endothelium-independent vasodilator, infusions in 190 hypertensive patients stratified according to dipper and nondipper status. The FBF was measured by strain-gauge plethysmography. Effects of oxidative stress on FBF were evaluated by intraarterial infusion of vitamin C. Ambulatory BP monitorings were obtained by a validated oscillometric device (SpaceLabs 90207 Monitor Inc., Issaquah, WA, USA).

Results: Systolic and diastolic blood pressures were higher during daytime and lower during night-time in dipper subjects than in nondippers. The peak percent increase in ACh-stimulated FBF was higher in dippers than in nondippers (473% vs. 228%, P < 0.001). The FBF responses to SNP were similar in dipper and nondipper patients. The FBF response to ACh during coinfusion of vitamin C was higher in nondippers rather than in dipper hypertensives.

Conclusions: Present data demonstrate that endothelium-dependent vasodilation is impaired in patients who have nondipper hypertension. The effects of vitamin C on impaired ACh-stimulated vasodilation support the hypothesis that oxidative stress contributes to endothelial dysfunction of nondipper hypertensive patients.