Expression, localisation and function of ACE and chymase in normal and atherosclerotic human coronary arteries

The expression, localisation and function of enzymes responsible for the local formation of angiotensin II in atherosclerotic and non-atherosclerotic human coronary arteries were studied. Human epicardial coronary arteries expressed mRNA for both ACE and chymase. Immunohistochemical studies revealed that ACE was localised to the vascular endothelium, and to a lesser extent the medial smooth muscle cells, in both large and small arteries. Chymase was detected in both types of vessel but was shown to be associated with mast cells. The contractions to angiotensin I in large arteries were inhibited only by a combination of quinaprilat and soyabean trypsin inhibitor. In the intramyocardial arteries the response to angiotensin I was markedly inhibited in the presence of chymostatin. These findings demonstrate that a dual pathway for the synthesis of angiotensin II is active in diseased and non-diseased coronary arteries.