Effect of endothelin on angiotensin converting enzyme activity in cultured vascular smooth muscle cells.

We evaluated the effect of endothelin-1(ET) on the angiotensin converting enzyme (ACE) activity in rat aortic smooth muscle cells (VSMCs). ACE activity was determined by radioimmunoassay of the amount of angiotensin II generated after the addition of angiotensin I (500 pg/ml) to cultured VSMCs. The antibody used had less than 0.1% cross-reactivity with angiotensin 1. ACE activity increased 1.9-fold 5 hr after the addition of 10−6 M ET under serum-free conditions. This stimulatory effect of ET on ACE activity in VSMCs was completely inhibited by 10-7 M captopril. Results suggested that the ACE present in SMCs is stimulated by ET.