Changes in Vascular Distensibility during Angiotensin-Converting Enzyme Inhibition Involve Bradykinin Type 2 Receptors

Changes in arterial stiffness and structure occur during cardiovascular diseases and can be modified by angiotensin-converting enzyme (ACE) inhibitors. In the present study we investigated the role of membrane-bound ACE (t-ACE) in the regulation of arterial structure and mechanics. Large and small arteries of t-ACE-/- mice were isolated to determine the passive pressure-diameter relationship. We observed that t-ACE-/- mice exhibit a reduced arterial distensibility compared to t-ACE+/+ mice. This reduced arterial distensibility was also observed after 9 weeks of captopril treatment (80 mg/kg/ day). We hypothesized that bradykinin type 2 receptor (BK(2)) stimulation might be involved in the regulation of arterial stiffness. t-ACE-/- and t-ACE+/+ mice were treated with Hoe 140 (1 mg/kg/day) for 14 days. After Hoe 140 treatment, both the structural and mechanical changes observed in the t-ACE-/- carotid artery were abolished. Although Hoe 140 administration increased blood pressure in both groups by approximately 10 mm Hg, the pressure difference between the two groups did not change. Thus, t-ACE is involved in the regulation of arterial distensibility. The changes observed in t-ACE-/- mice are not caused by an altered fetal development. Moreover, it is likely that the regulation of arterial distensibility by ACE involves stimulation of the BK(2) receptor.