ObjectivesTo investigate if antihypertensive treatment could improve endothelium-dependent vasodilatation in hypertensive patients, and whether the angiotensin II subtype-1 (AT1)-receptor antagonist irbesartan and the β1-receptor antagonist atenolol would differ in this respect.Subjects and methodsThirty-four patients (28 men and six women) with mild-to-moderate essential hypertension (diastolic blood pressure 90–120 mmHg) were randomized to once daily 150–300 mg irbesartan or 50–100 mg atenolol in a double-blind fashion, preceded by a placebo run-in period. Forearm blood flow (FBF) was assessed by venous occlusion plethysmography during local intra-arterial infusions of methacholine and sodium nitroprusside, to evaluate endothelium-dependent and endothelium-independent vasodilatation, respectively. Measurements of FBF were undertaken at the end of the run-in placebo period and repeated after 3 months of active antihypertensive treatment.ResultsIrbesartan and atenolol induced a similar decline in blood pressure (from 171/107 to 158/98 mmHg,P< 0.05), and improved endothelium-dependent vasodilatation (e.g. an increase in FBF response to 4 μg/min methacholine from 325±29% to 411±41%,P<0.05), with no difference between the two study drugs. No significant changes in endothelium-independent vasodilatation were induced by irbesartan or by atenolol.ConclusionsThe present study shows that 3 months of antihypertensive therapy with irbesartan or atenolol improves endothelium-dependent vasodilatation.