Increased activity of vascular ACE related to atherosclerotic lesions in hyperlipidemic rabbits.

The relationship between vascular angiotensin-converting enzyme (ACE) activity in the aorta and atherosclerotic lesions was investigated in rabbits fed two atherogenic diets, 0.5 and 1.5% cholesterol, for 17 wk. Tissue ACE activity was assessed by the cleavage rate of hippuric acid from a synthetic substrate. Total cholesterol, triglycerides, and phospholipids in the serum were significantly increased by the diet. Vascular ACE activity in the femoral artery, abdominal aorta, and aortic arch was significantly increased (2-5 times) by the atherogenic diet in a high-cholesterol-related manner compared with the rabbits fed a normal diet. The increase was associated with vascular heterogeneity of regions. There was a significant correlation between plaque area and vascular ACE activity in the aortic arch isolated from rabbits fed the higher (1.5%)-cholesterol diet. Contractile responses of the femoral artery to angiotensin I and II in the atherogenic diet-fed rabbits did not differ from those in animals fed the normal diet. It is conceivable that increased ACE in the vascular walls is involved in hyperlipidemia-induced atherogenesis, presumably through production of growth or stimulating factor(s) contributing to plaque formation.