Endothelium-dependent vasodilatation in treated and untreated hypertensive subjects

It has repeatedly been shown that endothelium-dependent vasodilatation (EDV) is impaired in patients with untreated hypertension. The effect of antihypertensive treatment on EDV has, however, not been extensively investigated. In the present study, EDV and endothelium-independent vasodilatation (EIDV) were studied in 20 untreated and 41 treated hypertensive subjects and in 26 matched, normotensive controls by means of infusion of methacholine (MCh), 2 and 4 microg/min, evaluating EDV, and nitroprusside (SNP), 5 and 10 microg/min, evaluating EIDV, in the brachial artery. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. The vasodilatory action of MCh was impaired in untreated hypertensives compared with controls, with the response in the treated hypertensives in between the other two groups (p < 0.01 vs both of the other groups). EIDV, on the other hand, was enhanced in the treated hypertensives (p < 0.01), so that the MCh to SNP FBF ratio, an index of endothelial function, was attenuated in both treated and untreated hypertensives (0.97 +/- 0.24 and 0.96 +/- 0.15, respectively), compared with controls (1.27 +/- 0.29, p < 0.001). Both EDV and EIDV declined with increasing number of antihypertensive drugs used in the treated hypertensives (p < 0.05). In conclusion, the endothelial function index was found to be similarly depressed in both treated and untreated hypertensive subjects compared with normotensive controls. Antihypertensive therapy seems to improve the vasodilatory capacity in general rather than enhancing endothelial function.