Expression of cardiac angiotensin-converting enzyme after myocardial infarction

目的：确定血管紧张素转换酶（ＡＣＥ）在心肌梗死后左心室组织修复及重构过程中，以及在假手术大鼠心肌中的分布．方法：在冠状动脉结扎后２４ｈ，１ｗｋ，２ｗｋ，３ｗｋ，６ｗｋ后用抗ＡＣＥ单克隆及多克隆抗体通过免疫组化染色显示心脏组织ＡＣＥ在上述时间点的表达．通过免疫荧光双染色法进一步明确是哪一种细胞表达ＡＣＥ．结果：在正常的心脏组织中ＡＣＥ染色局限在内皮细胞上，其密度随着血管树的分级呈阶梯状变化：小动脉的全部血管内皮细胞都有ＡＣＥ染色，毛细血管内皮细胞仅有约２０％有ＡＣＥ染色，静脉内皮细胞则完全没有ＡＣＥ染色．心肌梗死３ｗｋ后梗死区的坏死组织已被肉芽组织所取代并可观察到非常明显的ＡＣＥ过度表达；心肌梗死６ｗｋ后ＡＣＥ染色区缩小，在有大量胶原沉积的区域仅可见微弱的染色．绝大部分在ＡＣＥ高表达区表达ＡＣＥ的细胞是内皮细胞，少量巨噬细胞上也有ＡＣＥ染色．结论：在正常心脏组织中，内皮细胞表达ＡＣＥ的程度与细胞所处的解剖位置有关．心肌梗死后ＡＣＥ在梗死区的组织修复过程中有过度表达，其高峰在梗死后３ｗｋ，过度表达的ＡＣＥ主要来源于内皮细胞．

AIM: To localize cardiac angiotensin converting enzyme (ACE) during left ventricular repair after myocardial infarction (MI). METHODS: Cardiac ACE was examined by immunohistochemical staining using monoclonal and polyclonal antibodies against ACE 24 h, 1 wk, 2 wk, 3 wk, and 6 wk after coronary artery ligation in rats. Immunofluorescent double staining technique was applied to distinguish the cells which express ACE. RESULTS: ACE staining was confined 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 absent in the veins. One week after MI, ACE expression was noted in the granulation tissue. Three weeks after MI, necrosis within the infarction was replaced by granulation tissue and fibrous tissue which showed strong over expression of ACE. Six weeks after MI, the region with positive ACE staining regressed and the area with high collagen content on the endocardial side showed only weak ACE stain. Most of the ACE positive cells in the ACE over expression area were endothelial cells. A few macrophages seen in these regions were also ACE positive. CONCLUSION: Cardiac ACE was over expressed during the process of tissue repair following MI, reaching a peak in 3 wk. Endothelial cells took the most part of ACE expression.