ABSTRACT
Most patients subjected to coronary artery bypass grafting develop graft occlusions in some time after successful coronary surgery. Causes of graft occlusions comprise hyperplasia of intima occurring as a response to release of cytokines and angiotensin II. Angiotensin II is formed in human body with participation of angiotensin converting enzyme (ACE) or chymase. We found high concentrations of ACE in some smooth muscle cells in hyperplasia zone. Proliferation of smooth muscle cells, their hypertrophy and increased synthesis of intercellular space proteins facilitate graft occlusion. Moreover ACE was found in cytoplasm of macrophages infiltrating graft's intima. Thus ACE can be an important contributor to the process of coronary artery bypass graft obstruction.