Exclusion criteria include: (1) subjects without hypertension who have baseline systolic blood pressure <100 mmHg, (2) severe hypertension (blood pressure must be well-controlled on 3 antihypertensive agents or <150/100 mmHg on £2 antihypertensive agents), (3) ischemic changes on resting electrocardiogram, (4) clinical evidence of heart disease, cerebrovascular or peripheral vascular disease, (5) significant cardiac arrhythmias, (6) aortic stenosis, (7) 2nd or 3rd degree atrio-ventricular block, sinus node disease, or symptomatic bradycardia, (8) bronchospastic lung disease with active wheezing, (9) known hypersensitivity to any of the study drugs, (10) any contraindication to MRI, (11) serum creatinine ³ 1.5 mg/dL, (12) serum potassium ³ 5.0 mmol/L, (13) current smoker, (14) Serum transaminases greater than twice the upper limit of normal, (15) a history of gout, (16) pregnancy, and (17) other active medical problems detected by examination or laboratory testing.