Enalapril suppresses normal accumulation of elastin and collagen in cardiovascular tissues of growing rats.

We have investigated the effect of enalapril, an angiotensin converting-enzyme (ACE) inhibitor, on the accumulation of ventricular and vascular collagen and elastin in young, growing rats. Beginning at either 4 or 10 wk of age, male Wistar rats were treated with enalapril for 2 or 5 wk. Enalapril treatment had no significant effect on body weight and small, generally non-significant effects on systolic and diastolic blood pressures. In contrast, young enalapril-treated animals showed a marked decrease in accumulation of total elastin and collagen in both large (aorta, renal, and carotid) and smaller (superior and large mesenteric) arteries, as well as a large reduction in total collagen in both left and right ventricles. This effect also was present but less pronounced in rats treated with enalapril beginning at 10 wk of age. These data indicate that inhibition of ACE activity during a period of rapid growth significantly reduces accumulation of vascular and ventricular connective tissue and suggests that angiotensin II may be important in normal cardiovascular development and growth.