Dostal D E, Rothblum K N, Conrad K M, Cooper G R, Baker K M
Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822.
Am J Physiol. 1992 Oct;263(4 Pt 1):C851-63. doi: 10.1152/ajpcell.1992.263.4.C851.
Angiotensin II (ANG II) is a stimulus for positive chronotropic and inotropic effects, protein synthesis, and hypertrophic growth in cardiac tissue. These short- and long-term effects of ANG II are mediated through specific plasma membrane receptors. Indirect evidence suggests that ANG II synthesized in the myocardium may be important in regulating cardiac function. The cell types in the myocardium that produce components of the renin-angiotensin system have not been determined. In this study, we evaluated whether cultured cardiomyocytes and fibroblasts obtained from ventricles of neonatal rat hearts were capable of synthesizing ANG I and II. Both cardiomyocytes and fibroblasts were found to have immunofluorescent staining for ANG I, ANG II, and angiotensin-converting enzyme (ACE). The amounts of ANG I and II in cell extracts and conditioned media obtained from cardiomyocytes and fibroblasts were quantified by radioimmunoassay. The amounts of ANG I and II detected in cardiomyocyte cultures (1.48 x 10(6) cells/dish) were 32.2 +/- 16.2 (n = 4) and 6.2 +/- 2.9 (n = 4) ng/10(6) cells, respectively. The amounts of ANG I and II detected in the media conditioned by a 48-h exposure to cardiomyocytes were 5.2 +/- 1.2 (n = 3) and 2.1 +/- 1.2 (n = 3) ng/10(6) cells, respectively. The amounts of ANG I and II detected in fibroblast cultures (5.38 x 10(6) cells/dish) were 34.8 +/- 4.9 (n = 4) and 8.0 +/- 3.5 (n = 4) ng/10(6) cells, respectively. The amounts of ANG I and II obtained from media conditioned by a 48-h exposure to fibroblasts were 4.7 +/- 0.6 (n = 4) and 3.3 +/- 2.1 (n = 4) ng/10(6) cells, respectively. The identity of the radioimmunoassayable materials as ANG I and II peptides was confirmed in cardiomyocytes using an in vitro bioassay based on displacement of 125I-ANG II from receptor binding sites in cardiac membranes prepared from neonatal pig heart. Identification of ANG I and II and ACE in vitro in cultures of cardiac myocytes and fibroblasts supports the hypothesis that there is an intracardiac renin-angiotensin system that produces these peptides.
血管紧张素II（ANG II）可刺激心肌组织产生正性变时性和变力性作用、促进蛋白质合成以及引发肥厚性生长。ANG II的这些短期和长期效应是通过特定的质膜受体介导的。间接证据表明，心肌中合成的ANG II可能在调节心脏功能方面发挥重要作用。心肌中产生肾素-血管紧张素系统成分的细胞类型尚未确定。在本研究中，我们评估了从新生大鼠心室获取的培养心肌细胞和成纤维细胞是否能够合成ANG I和ANG II。结果发现，心肌细胞和成纤维细胞对ANG I、ANG II和血管紧张素转换酶（ACE）均有免疫荧光染色。通过放射免疫测定法定量检测心肌细胞和成纤维细胞提取物及条件培养基中ANG I和ANG II的含量。在心肌细胞培养物（每培养皿1.48×10⁶个细胞）中检测到的ANG I和ANG II含量分别为32.2±16.2（n = 4）和6.2±2.9（n = 4）ng/10⁶个细胞。经48小时心肌细胞处理的条件培养基中检测到的ANG I和ANG II含量分别为5.2±1.2（n = 3）和2.1±1.2（n = 3）ng/10⁶个细胞。在成纤维细胞培养物（每培养皿5.38×10⁶个细胞）中检测到的ANG I和ANG II含量分别为34.8±4.9（n = 4）和8.0±3.5（n = 4）ng/10⁶个细胞。经48小时成纤维细胞处理的条件培养基中获得的ANG I和ANG II含量分别为4.7±0.6（n = 4）和3.3±2.1（n = 4）ng/10⁶个细胞。利用基于从新生猪心脏制备的心脏膜受体结合位点上125I-ANG II置换的体外生物测定法，在心肌细胞中证实了放射免疫可检测物质为ANG I和ANG II肽。在心肌细胞和成纤维细胞培养物中对ANG I、ANG II和ACE进行体外鉴定，支持了存在一个产生这些肽的心脏内肾素-血管紧张素系统这一假说。
