Circadian variation of blood pressure and endothelial function in patients with essential hypertension

OBJECTIVES: The purpose of this study was to evaluate the relationship between the circadian blood pressure (BP) rhythm and endothelial function in patients with essential hypertension. BACKGROUND: Hypertension is associated with alterations in resistance artery endothelial function. Patients with a non-dipper circadian pattern of BP have a greater risk of cerebrovascular and cardiovascular complications than do patients with a dipper circadian pattern. METHODS: We evaluated the forearm blood flow (FBF) response to intra-arterial acetylcholine (ACh), an endothelium-dependent vasodilator, and isosorbide dinitrate (ISDN), an endothelium-independent vasodilator, infusion in 20 patients with non-dipper hypertension and 20 age- and gender-matched patients with dipper hypertension. The FBF was measured using a mercury-filled Silastic strain-gauge plethysmograph. RESULTS: The 24-h systolic BP, as well as nocturnal systolic and diastolic BPs were higher in non-dipper patients than in dipper patients. The 24-h urinary excretion of nitrite/nitrate and cyclic guanosine monophosphate was lower in non-dippers than in dippers. The response of FBF to ACh was smaller in non-dippers than in dippers (25.1 +/- 3.1 vs. 20.2 +/- 3.0 ml/min/100 ml tissue, p < 0.05). The FBF response to ISDN was similar in dippers and non-dippers. The FBF response to ACh was similar in the two groups following intra-arterial infusion of the nitric oxide (NO) synthase inhibitor N(G)-monomethyl-L-arginine. CONCLUSIONS: These findings suggest that endothelium-dependent vasodilation is blunted through a decrease in NO release in non-dippers compared with patients who have dipper hypertension.