Expression of cardiac angiotensin-converting enzyme after myocardial infarction

AIM: To localize cardiac angiotensin-converting enzyme (ACE) during left ve ntricular repair after myocardial infarction ( MI). METHODS: Cardiac ACE wa s examined by immunohistochemical staining using monoclonal and polyclonal antibodies against ACE 24 h, I wk, 2 wk, 3 wk, and 6 wk after coronary arte ry ligation in rats. Immunofluorescent double staining technique was applie d to distinguish the cells which express ACE. RESULTS: ACE staining was con fined to the endothelial cells and distributed in normal cardiac tissue in a gradient pattern along the vascular tree: present around the whole circle of arterial endothelium, present in about 20 % of the capillaries, and abs ent in the veins. One week after MI, ACE expression was noted in the granul ation tissue. Three weeks after MI, necrosis within the infarction was repl aced by granulation tissue and fibrous tissue which showed strong over-expr ession of ACE. Six weeks after MI, the region with positive ACE staining re gressed and the area with high collagen content on the endocardial side sho wed only weak ACE stain. Most of the ACE-positive cells in the ACE-over-exp ression-area were endothelial cells. A few macrophages seen in these region s were also ACE-positive. CONCLUSION: Cardiac ACE was over expressed during the process of tissue repair following MI, reaching a peak in 3 Wk. Endoth elial cells took the most part of ACE expression.