Localization of angiotensin converting enzyme in rat heart

Angiotensin converting enzyme (ACE) was localized in rat heart by quantitative in vitro autoradiography with 125I-351A as the radioligand. The binding association constant (KA) of the radioligand was measured in membrane-rich fractions of atrium, ventricle, and lung by a radioinhibitor binding assay. A single class of high-affinity binding sites was detected in each tissue, and a significant difference was found between KA values for atria and ventricles with a rank order of atria greater than lungs greater than ventricles. For autoradiography, coronal sections (10 micron) of the frozen heart were incubated with 125I-351A and exposed to x-ray film. The autoradiographs were quantitated by computerized image analysis. The highest density of ACE in the heart was found on valve leaflets (aortic, pulmonary, mitral, and tricuspid), which contrasted markedly with very low ACE labeling in the endocardium. The coronary arteries also showed dense labeling of ACE. The right atrium had a moderate density of ACE, which was higher than the left atrium and the ventricles. Both the endothelial and adventitial layers of the aorta and pulmonary artery displayed high densities of ACE, with very low density in the media. ACE was not detected in either the sinoatrial node or atrioventricular node. These results reveal a markedly nonuniform localization of ACE in the rat heart and suggest possible sites for local angiotensin II generation and bradykinin or other peptide metabolism.     

Increase of angiotensin converting enzyme gene expression in the hypertensive aorta.

To investigate the possible role of vascular angiotensin converting enzyme (ACE) in the development and maintenance of hypertension, we examined aortic ACE messenger RNA (mRNA) levels in two-kidney, one clip (2K1C) hypertensive rats. The blood pressure was increased remarkably at 4 weeks (early stage) after clipping and remained elevated at 12 weeks (chronic stage). The aorta ACE mRNA levels were significantly elevated in both early and chronic stages concurrently with the increases in aortic ACE activity and blood pressure. The plasma renin activity rose markedly at 4 weeks, but returned to the normal level at 12 weeks. Neither ACE activity in the lung and plasma, nor ACE mRNA level in the lung was altered at either stage. The aorta and liver angiotensinogen mRNA levels and renal renin mRNA level were increased at 4 weeks but decreased at 12 weeks. These results indicate that the acceleration of all components in the renin-angiotensin system may contribute to the development of 2K1C hypertension in the early stage. In the chronic stage, the increased vascular ACE induced by the elevated ACE mRNA levels in the aorta may play the primary role in the acceleration of local angiotensin II formation and thus may sustain the hypertension.     

血管紧张素转换酶基因多态性和动态血压关联性的初步探讨

探讨血压和位于人染色体１７ｑ２３的血管紧张素转换酶（ＡＣＥ）基因第１６内含子的一个２８７片段的插入／缺失多态性的关联性。在６０例６０岁以上的高血压病患者中，测量了偶测血压（ＣＢＰ）和动态血压（ＡＢＰ）；观察三种基因型之间的血压差异。结果显示：在三种基因型之间，未发现ＣＢＰ的明显差异（Ｐ＞０．０５），然而，其间的多个２４小时动态血压参数之间存在明显的不同（Ｐ＜０．０５）。本研究提示：ＡＣＥ基因的Ｉ／Ｄ多态性对血压有影响；ＡＢＰ较ＣＢＰ敏感。     

Tissue-specific activation of cardiac angiotensin converting enzyme in experimental heart failure.

In addition to the circulating renin-angiotensin system, recent data demonstrate the existence of tissue renin-angiotensin systems that may be important in cardiovascular homeostasis. However, the relative activities of the circulating and tissue renin-angiotensin systems have not been examined previously in pathophysiological states, such as congestive heart failure. The present study was performed to examine the status of plasma and tissue angiotensin converting enzyme (ACE) activities in compensated experimental heart failure induced by coronary artery ligation in the rat. Three groups of male Sprague-Dawley rats were examined: 1) nonoperated rats (NO, n = 5), 2) sham-operated rats (SO, n = 5), and 3) heart failure rats (HF, n = 11). Rats were studied an averaged of 85 days postoperatively. In HF animals, plasma renin concentration and serum ACE activities were not different compared with NO and SO control animals. Cardiac ACE activity was 50% greater in the right ventricle than the interventricular septum in NO and SO rats. Both right ventricular and interventricular septal ACE activity increased approximately twofold in HF animals as compared with NO and SO groups (p less than 0.05). In contrast, pulmonary, aortic, and renal ACE activities were not altered in HF rats compared with control animals. A positive correlation existed between the histopathological size of myocardial infarction and the level of right ventricular ACE activity (r = 0.75, p less than or equal to 0.05). Such a relation between infarct size and either serum or noncardiac tissue ACE activities was not observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

心房颤动患者心房组织的血管紧张素转换酶2表达及血管紧张素转换酶抑制剂干预的影响

目的 探讨心房颤动（房颤）患者心房肌组织中血管紧张素转换酶2（ACE2）的表达和血管紧张素转换酶抑制剂（ACEI）干预的影响及可能的信号传导途径。方法 选取接受开胸手术的风湿性心脏病患者47例,手术中取右心耳处心房肌标本。采用RT-PCR法检测心房肌ACE2和ACEmRNA水平,采用Western blot法检测ACE、ACE2、细胞外信号调节激酶1／2（ERK1／2）和磷酸化的细胞外信号调节激酶1／2（pERK1／2）蛋白表达水平,应用放射免疫法检测心房肌组织血管紧张素Ⅱ（AngⅡ）水平。结果 与窦性心律组相比,持续性房颤组心房肌组织中ACE2表达显著减少（P〈0．05）,而ACE的表达和AngⅡ含量显著增加（P〈0．05）。ERK1／2的活化水平在持续性房颤组较窦性心律组明显增加（P〈0．05）。与持续性房颤组相比,ACEⅠ干预组ACE2表达水平显著增加（P〈0．01）,ERK1／2的活化水平显著降低（P〈0．05）,而ACE表达和AngⅡ含量差异无统计学意义。结论 房颤患者心房肌组织中ACE2表达下调,ACE／ACE2平衡失调;ACEⅠ对房颤的长期临床效应可能与其上调ACE2、抑制有丝分裂素激活蛋白激酶信号途径有关。     

Renin and angiotensin converting enzyme in elasmobranchs.

Renin-like activity (RLA) and angiotensin I converting enzyme-like activity (ACELA), the two key enzymes of the renin-angiotensin system (RAS), were sought in the elasmobranch Scyliorhinus canicula. Renal extracts were desalted in a G-25 and eluted in a G-100 Sephadex column (calibration 15,000-70,000). The fractions were concentrated in a vacuum device. A 48,000-MW fraction incubated with synthetic and porcine angiotensiongen generated angiotensin I estimated by RIA. This same fraction was vasopressor in rats and dogfish. ACELA was sought in gill, heart, liver, spleen, pancreas, intestine, kidney, gonads, brain, skin, and muscle of dogfish using a spectrophotometric assay. The highest level of ACELA was found in the gills followed by spleen, kidney, and brain (33.79 +/- 2.3, 29.56 +/- 1.0, 14.62 +/- 1.0, and 13.80 +/- 2.3 nmol hippurate/min/mg protein, respectively). Intestine, gonads, skin and muscle contained no measurable amounts of ACELA. Captopril inhibited enzymatic activity from all ACELA containing tissues.     

Hypoxia does not alter angiotensin converting enzyme activity in hamster pulmonary microvessels

Studies were initiated to investigate the effects of hypoxia on the conversion of angiotensin I (AI) to angiotensin II (AII) in microvessels of the lung. Using the technique of allografting neonatal lung tissue into the cheek pouch of normal hamsters, the microvessels of the lung, pulmonary arterioles, and venules could be visualized and manipulated by direct in vivo microscopy. The microvessels of the lung were studied 7-10 days after allografting by anesthetizing the hamster with pentobarbital (6.0 mg/100 g body weight i.p.) and then preparing the lung tissue for observation. The tissue was suffused with a Ringer's bicarbonate solution bubbled with a normal (20% O2-5% CO2-75% N2) or a low (95% N2-5% CO2) oxygen mixture. After equilibration, a pulmonary arteriole or venule was selected for observation, and the vessel geometry was recorded. Then, a micropipette containing either AI or AII was positioned alongside the vessel, and the agent was delivered continuously for 2 minutes. Lumen diameter was recorded continually for 8-10 minutes. This procedure was repeated until both angiotensins were tested on pulmonary arterioles and venules under conditions of a normal and low oxygen environment. This protocol was repeated on cheek pouch microvessels that did not contain pulmonary allografts. Both AI and AII produced rapid decreases in the lumen diameters of all microvessels tested. This vasoconstriction was greater for AII, and the oxygen environment did not alter the response. Conversion of AI to AII was not altered by the oxygen environment, and the relative conversion was similar in the microvessels of the lung and cheek pouch.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enhanced cardiac angiotensinogen gene expression and angiotensin converting enzyme activity in tachypacing-induced heart failure in rats

Summary The aim of the study was to analyze changes in myocardial angiotensinogen gene expression and myocardial angiotensin converting enzyme activity in slowly progressing low-output failure. In adult, male Wistar rats, acute ventricular tachypacing by 610 to 620 impulses per minute lowered enddiastolic external diameter of the left ventricle by 2.6% (p < 0.01), but did not lower cardiac output or abolish coronary reserve, since left-ventricular subendocardial blood flow of paced rats increased under dipyridamole (2 mg/kg i.v.) by 56% (p < 0.01). Systemic neuroendocrine activation and ventricular dilation without enlargement of ventricular mass developed subsequent to chronic tachypacing, but left-ventricular diameter during pacing never exceeded the value of sham rats on sinus rhythm. After 2 weeks, cardiac output was lowered by 14% (p < 0.001), cardiopulmonary blood volume was elevated by 30% (p < 0.001), and angiotensinogen mRNA and angiotensin converting enzyme activity in ventricular myocardium were doubled. We conclude that conditions for an enhanced intracardiac angiotensin II-formation developed in tachypacing-induced heart failure, but that enhanced . systolic wall stress or myocardial ischemia are not required for this activation of the local cardiac reninangiotensin system.     

糖尿病仓鼠心肌糜蛋白酶和血管紧张素转换酶基因表达的变化

目的观察糖尿病仓鼠心肌血管紧张素Ⅱ(ATⅡ)含量,糜蛋白酶和血管紧张素转换酶(ACE)基因表达变化,探讨糜蛋白酶和ACE在糖尿病心肌病变发生中的作用。方法测定正常对照(NC)组(n=10)和糖尿病(DM)组(n=10)仓鼠血浆和心肌ATⅡ含量;荧光定量PCR检测心肌糜蛋白酶和ACE基因表达;观察心肌Ⅰ、Ⅲ型胶原含量变化;测定血糖、糖化血清蛋白、血脂和胰岛素水平。结果与NC组相比,DM组仓鼠心肌Ⅰ、Ⅲ型胶原表达量分别为NC组的2.71和1.68倍,且Ⅰ/Ⅲ型胶原比值明显升高;心肌局部ATⅡ含量显著升高;糜蛋白酶基因表达显著高于NC组,而ACE基因表达在两组间差异无统计学意义。结论糖尿病仓鼠心肌病变时心肌局部升高的ATⅡ可能主要来源于糜蛋白酶途径,抑制糜蛋白酶的表达或活性可能对糖尿病心肌病变具有治疗价值。     

Effect of pressure overload on angiotensin receptor expression in the rat heart during early postnatal life

The development of cardiac hypertrophy during neonatal life and in adults implies different processes. The angiotensin II (Ang II) system is involved in the development of cardiac hypertrophy in adults, but its role in neonates remains unclear. The aim of this study was to estimate the influence of increased hemodynamic load on the developmental pattern of the AT1/AT2 receptor expression in the heart. Two-day-old rats submitted to abdominal aortic constriction (AC) or sham operation were sacrificed 2 h, and 1, 3, and 8 days after surgery. Ang II was evaluated in sera and immunohistology was performed to define the cardiac hypertrophy process. The Ang II receptor subtypes 1 and 2 were quantified at the receptor and mRNA levels by(125)I-Ang II binding and RT-PCR, respectively. Ang II content in sera increased transiently 2 h after surgery in the AC group. In sham-operated, AT1 and AT2 decreased throughout the period studied at both mRNA and receptor levels. However, the AT1 mRNA level decrease was more pronounced than that of AT2 (by 57% and 27%, respectively). AC not only prevented the postnatal decrease in AT mRNA level but resulted in an increase in AT1 mRNA 8 days after surgery (P<0.05). Besides in the AC groups, AT2 mRNA levels but not those of AT1 mRNA were linearly correlated with the left ventricular mass. At the receptor level, a significant transient (1 day after surgery) increase in both AT1 and AT2 was observed. In conclusion, our data demonstrated that imposition of pressure overload soon after birth altered the pattern of AT receptor expression.     

Modification of hemodynamics by angiotensin converting enzyme inhibitors in heart failure

Challenge to a new therapeutic principle to treat heart failure is to ameliorate or eliminate symptoms, decelerate progression of the disease and reduce mortality. However, to begin, one would request improvement of objective hemodynamic parameters. Angiotensin converting enzyme (ACE) inhibitors may have acute and chronic, global and regional effects. ACE inhibitors acutely and chronically reduce pre- and afterload without reflex tachycardia. They lower myocardial oxygen consumption and improve the relation of coronary blood flow to myocardial oxygen consumption. Cerebral and renal blood flow generally are beneficially influenced if the blood pressure is not lowered too much. Left ventricular dilatation following extensive myocardial infarction which is prognostically unfavourable, may be retarded or prevented by ACE-inhibitors. It is not yet clear whether mortality may thus be reduced as in patients with severe heart failure. Large multicenter studies currently address this question. It is unclear as well whether the effects of ACE-inhibitors are exclusively due to a reduction of circulating angiotensin II. Most likely, interference is of major importance with local renin-angiotensin systems, other hormone systems and the central and peripheral nervous system.     

Serum angiotensin converting enzyme in respiratory diseases.

More than 1700 estimations of serum angiotensin converting enzyme (SACE) were undertaken, mostly in respiratory disorders, to assess its value as a specific and/or a sensitive indicator of different diseases. Though highest levels were found in lepromatous leprosy consistently, it was also found almost always elevated in active stages of sarcoidosis. Since it is raised in a variety of respiratory disorders, it is not a specific diagnostic test. It is, however, a fairly sensitive index of disease activity in sarcoidosis whether on treatment or not. Sudden elevation, after a prolonged period of low or normal values may indicate relapse in sarcoidosis.     

Comparison between angiotensin receptor antagonism and converting enzyme inhibition in heart failure

This study was designed to assess the influence of the activation status of the renin angiotensin system (RAS) on the hemodynamic effects of EXP 3174 (an angiotensin AT1 receptor antagonist) and enalaprilat (an angiotensin converting enzyme inhibitor) in tachycardia-induced heart failure. Thirteen dogs were chronically instrumented to measure left ventricular (LV) pressure, its first time derivative (LV dP/dt), atrial and aortic pressures, and cardiac output. EXP 3174 (0.1 mg/kg, iv) or enalaprilat (1 mg/kg, iv) were administered in conscious dogs with heart failure induced by right ventricular pacing (250 beats/min, 3 weeks). EXP 3174 and enalaprilat produced significant vasodilation but the effects of EXP 3174 on mean aortic pressure (MAP), cardiac output, and total peripheral resistance (TPR) were only 50% of those produced by enalaprilat. When dogs were grouped according to their baseline plasma renin activity (PRA) values, in dogs with normal PRA (0.5 ± 0.1 ng/ml/h) EXP 3174 did not produce significant change in MAP and TPR, while enalaprilat decreased significantly MAP and TPR. In contrast, in dogs with high PRA (6.7 ± 3.2 ng/ml/h), EXP 3174 produced significant reductions in MAP and TPR, which were similar to those produced by enalaprilat. Thus, in conscious dogs with heart failure, enalaprilat is effective whether the RAS is activated or not. In contrast, EXP 3174 is effective only when the RAS is activated. These results may help in the choice of inhibitors of the RAS in heart failure. Received: 22 September 1998, Returned for revision: 14 October 1998, Revision received: 23 November 1998, Accepted: 8 December 1998     

Influence of angiotensin converting enzyme inhibition on relation of atrial natriuretic peptide concentration to atrial pressure in heart failure.

OBJECTIVE--To examine the influence of the duration of follow up on the values of heart rate variability (HRV) and the left ventricular ejection fraction (LVEF) for predicting mortality after infarction. BACKGROUND--HRV is an index of autonomic balance that identifies patients at a high risk of arrhythmic events. The index is most depressed during the first few weeks after myocardial infarction whereas left ventricular function tends to deteriorate with time. HYPOTHESIS--The value of depressed HRV measured before discharge from hospital for predicting mortality after infarction should decline with time. METHODS--The HRV and the LVEF were assessed in 433 survivors of a first acute myocardial infarction: HRV < 20 units and LVEF < 40% were taken as cut off points. Kaplan-Meier survival functions for total cardiac mortality and sudden cardiac death were calculated for the whole five year follow up period and for different intervening periods. RESULTS--During follow up of four weeks to five years there were 46 (10.6%) deaths and 15 (3.5%) patients died suddenly. Within the whole follow up period, HRV < 20 units and LVEF < 40% were both strongly associated with total cardiac mortality (p < 0.0001), but HRV was an independent predictor of total cardiac mortality only during the first six months of follow up. There were no deaths predicted by HRV < 20 units after the first year of follow up whereas LVEF < 40% had a sensitivity of 43% and a positive predictive accuracy of 9% for predicting death during this period. HRV < 20 units was better than LVEF < 40% in predicting sudden deaths during the first year of follow up but was an independent predictor only of those sudden deaths occurring within six months of infarction. CONCLUSIONS--The duration of follow up affects the prediction of sudden death and total cardiac mortality from HRV. Reduced HRV as measured before discharge from hospital does not seem to retain independent prognostic value after six months of follow up. These findings have potential implications for the serial evaluation of HRV and for the prevention of sudden death after myocardial infarction.     

血管紧张素转化酶-2研究进展

根据世界卫生组织预测,到2020年心血管疾病将成为导致死亡的主要原因[1]。我国高血压患病率逐年增高,严重影响了人民群众的身体健康[2]。高血压是心血管疾病最常见可转化的危险因子之一[3]。肾素-血管紧张素系统(renin-angiotensinsystem,RAS)被认为是有着强大生理功能的激素系统,对血压的调节、血液等内环境的稳定性、血管功能以及细胞生长起着重要作用,在各种心血管疾病和肾病病理生理过程中发挥着重要的功能[4]。从肾素-血管紧张素被作为一个整体的概念提出,对肾素-血管紧张素系统的研究已有30余年历史了。尽管如此,最近几年在这个原来…     

The multifacetted role of angiotensin converting enzyme inhibitors in congestive heart failure

The angiotensin converting enzyme (ACE) inhibitors constitute a major breakthrough in the medical management of congestive heart failure. The incidence of side effects with these agents is surprisingly low when they are used in the appropriate dosage. They produce sustained beneficial hemodynamic and symptomatic improvement in most patients with congestive heart failure and may produce greater symptomatic benefit than digoxin when given as second-line therapy to patients with heart failure on diuretics. Their neurohumoral effects generally are advantageous, resulting in normalization of sodium and potassium balance and a reduction in ventricular arrhythmias. The ACE inhibitors may improve survival in patients with congestive heart failure, and recent data suggest that they may prevent or delay the development of left ventricular dilatation and overt heart failure in patients with asymptomatic left ventricular dysfunction.     

血管紧张素转换酶及其基因多态性与血管性痴呆和阿尔茨海默病的关系研究

目的探讨血清血管紧张素转换酶(ACE)活性及ACE基因插入/缺失(I/D)多态性与血管性痴呆(VD)和阿尔茨海默病(AD)的关系。方法应用聚合酶链反应(PCR)检测2002年7月至2004年5月南京医科大学附属脑科医院和江苏大学附属第四医院62例VD、39例AD患者以及50名健康对照者ACE基因I/D多态性;对其中56例VD、33例AD患者和46名健康对照者以毛细管电泳法测定血清ACE活性,并进行统计学比较。结果VD组和AD组血清ACE活性与正常对照组相比差异无显著性意义;未发现ACE基因I/D多态性与VD的相关性;AD组I等位基因频率高于对照组,差异有显著性意义(P<0.05)。结论ACE基因I/D多态性与VD无相关性,ACEI等位基因可能是AD发病的危险因素。     

Elevated serum angiotensin I converting enzyme in sarcoidosis.

Serum angiotensin I converting enzyme was found to be elevated in 56 patients with sarcoidosis (52.7 +/- 25.4 nmole per min per ml) compared to 84 normal control subjects (28.2 +/- 11.3 nmole per min per ml), 22 patients with tuberculosis (26.4 +/- 10.9 nmole per min per ml), and 20 patients with lymphomas (31.8 +/ 13.9 nmole per min per ml). Forty-eight per cent of the patients with sarcoidosis had values of enzymatic activity that were higher than 2 SD above the mean value of the control population; the false-positive rate in all nonsarcoidosis subjects combined was 5.5 per cent. Patients with parenchymal disease with or without hilar adenopathy had values somewhat higher than those with hilar adenopathy alone, but the difference was not significant (P less than 0.1). Patients with a known duration of disease greater than 2 years also had somewhat higher values than those with known disease less than 2 years, but the difference was not significant (P less than 0.1). There was no significant difference in values for patients receiving or not receiving steroids.