Distinct effects of amlodipine treatment on vascular elastocalcinosis and stiffness in a rat model of isolated systolic hypertension

Objective Medial elastocalcinosis (MEC) contributes to the development of large artery stiffness and isolated systolic hypertension. Since endothelin receptor antagonists can prevent and regress elastocalcinosis, our aim was to determine whether amiodipine, a calcium channel blocker that inhibits endothelin signaling, could likewise influence MEC, or reduce pressure mainly through its vasorelaxing properties. Methods Control male Wistar rats were compared with rats receiving warfarin (20 mg/kg per day) with vitamin K, (15 mg/kg per day) alone (WVK) or in association with amlodipine (115 mg/kg per day) for 4 weeks or during the last week or last 4 weeks of an 8-week WVK treatment (two regression groups). Results Inactivation of matrix Gla protein by WVK for 4 or 8 weeks increased the calcium content 10-fold in the aorta, inducing a significant elevation of pulse wave velocity and pulse pressure by selective augmentation of systolic blood pressure. Amlodipine prevented aortic MEC, pulse wave velocity and pulse pressure elevation, but reversed only MEC and pulse pressure when administered for 4 weeks. One week of amlodipine administered after 7 weeks of WVK partially decreased pulse pressure without modifying aortic MEC. Amlodipine did not reduce the fibrosis associated with calcified areas in the WVK model during the regression protocols. Conclusion The clinical efficacy of amlodipine in improving hemodynamic variables and reducing cardiovascular events in isolated systolic hypertension could be explained by its beneficial effect on vascular calcification. Amlodipine's lack of effect on pulse wave velocity and collagen deposition, however, suggests that it may reduce pulse pressure by means other than improving arterial stiffness.