Urata H, Boehm K D, Philip A, Kinoshita A, Gabrovsek J, Bumpus F M, Husain A
Department of Cardiovascular Biology, Cleveland Clinic Foundation, Ohio 44195.
J Clin Invest. 1993 Apr;91(4):1269-81. doi: 10.1172/JCI116325.
The human heart is a target organ for the octapeptide hormone, angiotensin II (Ang II). Recent studies suggest that the human heart contains a dual pathway of Ang II formation in which the major Ang II-forming enzymes are angiotensin I-converting enzyme (ACE) and chymase. Human heart chymase has recently been purified and its cDNA and gene cloned. This cardiac serine proteinase is the most efficient and specific Ang II-forming enzyme described. To obtain insights into the cardiac sites of chymase-dependent Ang II formation, we examined the cellular localization and regional distribution of chymase in the human heart. Electron microscope immunocytochemistry using an anti-human chymase antibody showed the presence of chymase-like immunoreactivity in the cardiac interstitium and in cytosolic granules of mast cells, endothelial cells, and some mesenchymal interstitial cells. In the cardiac interstitium, chymase-like immunoreactivity is associated with the extracellular matrix. In situ hybridization studies further indicated that chymase mRNA is expressed in endothelial cells and in interstitial cells, including mast cells. Tissue chymase levels were determined by activity assays and by Western blot analyses. Chymase levels were approximately twofold higher in ventricles than in atria. There were no significant differences in chymase levels in ventricular tissues obtained from non-failing donor hearts, failing ischemic hearts, or hearts from patients with ischemic cardiomyopathy. These findings suggest that a major site of chymase-dependent Ang II formation in the heart is the interstitium and that cardiac mast cells, mesenchymal interstitial cells, and endothelial cells are the cellular sites of synthesis and storage of chymase. In the human heart, because ACE levels are highest in the atria and chymase levels are highest in ventricles, it is likely that the relative contribution of ACE and chymase to cardiac Ang II formation varies with the cardiac chamber. Such differences may lead to differential suppression of cardiac Ang II levels during chronic ACE inhibitor therapy in patients with congestive heart failure.
人类心脏是八肽激素血管紧张素II（Ang II）的靶器官。最近的研究表明，人类心脏存在Ang II形成的双重途径，其中主要的Ang II形成酶是血管紧张素I转换酶（ACE）和糜酶。人类心脏糜酶最近已被纯化，其cDNA和基因也已克隆。这种心脏丝氨酸蛋白酶是所描述的最有效和最特异的Ang II形成酶。为了深入了解糜酶依赖性Ang II在心脏中的形成部位，我们研究了糜酶在人类心脏中的细胞定位和区域分布。使用抗人糜酶抗体的电子显微镜免疫细胞化学显示，在心脏间质以及肥大细胞、内皮细胞和一些间充质间质细胞的胞质颗粒中存在糜酶样免疫反应性。在心脏间质中，糜酶样免疫反应性与细胞外基质相关。原位杂交研究进一步表明，糜酶mRNA在内皮细胞和包括肥大细胞在内的间质细胞中表达。通过活性测定和蛋白质印迹分析确定组织糜酶水平。心室中的糜酶水平比心房中大约高两倍。从非衰竭供体心脏、衰竭缺血心脏或缺血性心肌病患者心脏获得的心室组织中，糜酶水平没有显著差异。这些发现表明，心脏中糜酶依赖性Ang II形成的主要部位是间质，心脏肥大细胞、间充质间质细胞和内皮细胞是糜酶合成和储存的细胞部位。在人类心脏中，由于ACE水平在心房中最高，而糜酶水平在心室中最高，因此ACE和糜酶对心脏Ang II形成的相对贡献可能因心腔而异。这种差异可能导致充血性心力衰竭患者在慢性ACE抑制剂治疗期间心脏Ang II水平受到不同程度的抑制。
