Expression and function of angiotensin converting enzyme, chymase, and angiotensin II in the human radial artery and internal thoracic artery

Background. The potential role of the local renin-angiotensin system to dif ferentially affect radial artery and internal thoracic artery graft perform ance has not been examined. Methods, Contractile responses to angiotensin I and II in the radial artery and the internal thoracic artery were examined in vitro. The expression fu nction, and localization of angiotensin receptors, angiotensin converting e nzyme, and chymase were studied in radial artery and internal thoracic arte ry segments. Results. Angiotensin I and II contractions were significantly greater (p < 0.05) in the radial artery compared to the internal thoracic artery. In bot h arteries, angiotensin II responses were mediated via the AT(1) receptor. Messenger RNA transcripts for angiotensin-converting enzyme and chymase wer e detected in both arteries. Angiotensin-converting enzyme was localized to luminal and vase vasorum endothelial cells and smooth muscle cells in both vessels, while chymase was colocalized with mast cells in adventitial and medial layers. An angiotensin converting enzyme or a chymase inhibitor sing ularly had no effect on angiotensin I contractions, however, when combined, a marked inhibition of the angiotensin I response was observed in both ves sels. Conclusions. Our results illustrate the complexities which exist within the local renin angiotensin system and suggest that clinical trials which may modulate the system are warranted. (Ann Thorac Surg 2000;70:2054-63) (C) 20 00 by The Society of Thoracic Surgeons.