Effect of an angiotensin II receptor antagonist, candesartan cilexetil, on canine intima hyperplasia after balloon injury

Abstract

The roles of angiotensin (Ang) II as produced by two different enzymes, angiotensin-converting enzyme (ACE) and chymase, were investigated in a canine experimental model where intima hyperplasia was induced by balloon catheterization in the common carotid and femoral arteries. The animals received oral candesartan cilexetil (3 mg/kg) or enalapril (10 mg/kg) twice a day for 5 weeks. After 1 week of active drug therapy, the common carotid and femoral arteries were unilaterally injured by balloon catheterization. In the common carotid arteries, both ACE and chymase activities were increased by the injury, with the increase in chymase activities being greater than that in ACE activities. In the femoral arteries, ACE, but not chymase, activities were significantly increased by the injury. Both candesartan cilexetil and enalapril reduced blood pressure almost equally. Enalapril increased plasma renin activity more strongly than did candesartan cilexetil, and significantly decreased vascular and plasma ACE activities. Candesartan cilexetil significantly suppressed the formation of intima hyperplasia in both the carotid and femoral arteries, while enalapril significantly suppressed intima hyperplasia in the femoral, but not in the carotid arteries. These results indicate that local Ang II production by ACE and chymase is involved in the hyperplasia seen in injured intima, and the difference in the inhibitory action of candesartan and enalapril reflects the extent of contribution of each enzyme. The effect of the ACE inhibitor, enalapril, depended on the activity of ACE, whereas that of the Ang II receptor antagonist, candesartan, was independent of ACE activity.