Angiotensin converting enzyme activity is present in the endothelium-denuded aorta

Angiotensin converting enzyme activity was measured in intact aortic rings utilizing the synthetic tripeptide [3H]-benzoyl-Phe-Ala-Pro as the substrate. Intact aortic rings possessed angiotensin converting enzyme activity which was blocked by captopril. Enzyme activity was reduced by approximately 30% after removal of the endothelium by chemical or mechanical methods. The remaining activity was also captopril-sensitive. These results suggest that in addition to endothelium, angiotensin converting enzyme activity is present in other vascular cells and may contribute to the metabolism of angiotensin I generated within the vessel wall.