AGT and Hypertension: Aggravation of BP variability is attributable to several factors [19] (Fig. 1): Vascular factors include increase in the stiffness of the conduit arteries (i.e. the aorta and its major branches) by aging, hypertension, and atherosclerosis, decrease in the compliance of the resistant arteries/arterioles by hypertensive remodeling, and increase in vascular tonus of the resistance arteries/arterioles by increased sympatheticnerve activity and/or humoral factors, such as angiotensin II and endothelin.