Metabolism of bradykinin and angiotensin I by human basilar artery and rabbit aorta.

The role of angiotensin converting enzyme in the metabolism of bradykinin and angiotensin I by in vitro human basilar artery and rabbit aorta was studied. On both human basilar artery and rabbit aorta concentration-effects curves to angiotensin I were significantly attenuated by captopril at a concentration which had no effect on bradykinin responses on both tissues. The metabolism of bradykinin and angiotensin I was studied using high performance liquid chromatography. Both peptides were broken down by human basilar artery and rabbit aorta in a similar fashion. The breakdown of angiotensin I but not bradykinin was significantly attenuated by captopril. 1,10-phenanthroline did attenuate breakdown of bradykinin but this was found not to be significant compared with controls. The results confirm that angiotensin converting enzyme is present in both these tissues and is important for the conversion of angiotensin I to angiotensin II. It appears that other peptidases are important in the breakdown of kinins by these tissues and should be taken into account when investigating the mechanism of action of such peptides on these vascular preparations.