Improvement in Endothelial Function by Angiotensin-converting Enzyme Inhibition and Vitamin C in Essential Hypertension

Background and Objectives:The endothelium plays an important role in maintaining vascular tone and function. This essential hypertension may be associated with alterations in endothelial function. The effects of antihypertensive agents on endothelial function have not been fully evaluated in human hypertension and data on the forearm circulation of humans is controversial. The aim of this study was 1 to evaluate endothelial function in hypertensive patients 2 to investigate whether vitamin C administration has a benefit on endothelial function and 3 to determine whether treatment with ACE inhibitor improve improves endothelial dysfunction in hypertensive patients. Materials and Methods:The endothelial function was estimated using venous occlusion plethysmography (VOP in 8 hypertensive patients and 8 healthy volunteers. The patients in the hypertension group were treated with enalapril, then reexamined. The change of forearm blood flow (FBF was measured under conditions of acetylcholine infusion through the brachial artery as well as with intra- arterial vitamin C. The measurement of forearm volume change was repeated 7 times for each stage. Results:The forearm blood flow response to acetylcholine was significantly enhanced with inra-arterial infusion of vitamin C in the hypertensive group before antihypertensive treatment (302±58%→446±43%. Co-infusion of L-NMMA, an inhibitor of nitric oxide synthase, the blunted forearm blood flow response to acetylcholine (Vit C (+; 446±43%→Vit C+L-NMMA;229±23%. After Following antihypertensive treatment with enalapril for 2 months in the hypertensive group, endothelium-dependent vasorelaxation (vasodilatory response to acetylcholine was significantly improved in the treated group as compared to mea- surements taken before enalapril treatment (302±58%→643±78%. Conclusions:Although the mechanisms leading to depressed endothelial function in essential hypertension remains to be elucidated, our study shows