Role of Endogenous Angiotensin II and Prostaglandins in the Antihypertensive Mechanism of Angiotensin Converting Enzyme Inhibitor in Hypertension

The role of endogenous angiotensin II and prostaglandins (PGs) in the antihypertensive effect of converting enzyme inhibitor, captopril, was studied in essential hypertension by the separate and the combined administration of captopril and indomethacin. Although plasma angiotensin II was similarly suppressed by the separate and the combined administration of captopril and indomethacin, captopril lowered and indomethacin increased the mean blood pressure. There were negative correlations between the changes in mean blood pressure and in urinary sodium excretion as well as in urinary PGE excretion. These results suggest that endogenous PGs may be implicated in the antihypertensive effect of captopril through the alteration of sodium balance.     

血管紧张素转换酶基因多态性与血管紧张素转换酶抑制剂疗效的相关性

目的　研究原发性高血压 (EH)患者的血管紧张素转换酶 (ACE)基因多态性与血管紧张素转换酶抑制剂 (ACEI)疗效的相关性。方法　 ( 1)用ACEI对 5 17例EH患者进行为期 6周的降压治疗 ,所用药物为咪达普利或苯那普利。 ( 2 )用聚合酶链反应 (PCR)方法检测患者的ACE基因多态性 ,ACE基因有 3种表现型 :II型、DD型和DI型。 ( 3 )治疗前后及治疗过程中对患者的收缩压、舒张压和心率进行监测。结果　 ( 1)在总共 5 17例患者中 ,ACE基因型为DD者有 13 2人( 2 5 5 % ) ,II者有 13 0人 ( 2 5 2 % ) ,ID者有 2 5 5人 ( 4 9 3 % )。 ( 2 )不同基因型组间的性别、年龄、体重指数及心率等的差异无统计学意义。 ( 3 )在这三组患者中 ,治疗前后收缩压的降幅分别为 ( -14 5± 12 7)mmHg ,( -14 3± 13 1)mmHgand( -14 0± 12 2 )mmHg (P =0 94) ,舒张压的降幅分别为 ( -8 7± 7 4)mmHg ,( -8 7± 7 7)mmHgand ( -8 5± 6 7)mmHg (P =0 96)。结论　本研究没有发现EH患者的ACE基因多态性与ACEI的降压疗效相关 ,据此 ,不能根据EH患者的ACE基因型来指导ACEI的降压治疗     

Regulation of Prostacyclin Generation by Angiotensin Converting Enzyme Related Substances in Cultured Human Vascular Endothelial Cells

The regulation of prostacyclin (PGI₂) generation by angiotensin I-converting enzyme (ACE) related substances was investigated using cultured human vascular endothelial cells. Angiotensin I (AI) or bradykinin (BK) increased PGI₂ generation and ACE activity, while the ACE inhibitor, captopril decreased both of them, and angiotensin II (AII) did not show any effect. The increasing rate of PGI₂ generation induced by AI or BK was not affected by the pretreatment with captopril. These results suggest that the accumulation of AI or BK via the inhibition of ACE by captopril did not cause the enhancement of PGI₂ generation. Rather, it was proposed that the enhanced PGI₂ generation by AI or BK might be regulated by ACE activation derived from these substances, as an autoregulation mechanism.     

Possible Role of Vascular Angiotensin Converting Enzyme in the Genesis of Hypertension

This study was designed to evaluate changes in angiotensin converting enzyme (ACE) activity in 2-kidney, 1-clip renal hypertensive dogs. Blood pressure increased and remained elevated for eight months after partial clamping of the left renal artery. Plasma renin activity was increased for one month after surgery, but then returned to the pre-clamping level. SA-446, a potent ACE inhibitor, reduced blood pressure in 8 M-hypertensive dogs. Plasma ACE activities was not altered during the course of hypertension, but vascular ACE activities in the pulmonary and mesenteric arteries and the aorta were significantly increased in 8 M-hypertensive dogs. These results may indicate that ACE plays an important role in the maintenance of chronic phase of 2-kidney, 1-clip renal hypertension and that suppression of vascular ACE activities might be a mechanism underlying the hypotensive effect of ACE inhibitors.     

Effect of Losartan on Right Ventricular Hypertrophy and Cardiac Angiotensin I-Converting Enzyme Activity in Pulmonary Hypertensive Rats

The aim of this study was to investigate the effect of prophylactic treatment with the angiotensin type 1 (AT₁) receptor antagonist losartan on right ventricularhypertrophy and cardiac angiotensin I-converting enzyme (ACE) activity in a rat model of monocrotaline-induced pulmonary hypertension. Losartan failed to prevent either pulmonary hypertension or right ventricular hypertrophy. Right ventricular ACE in untreated pulmonary hypertensive rats did not differ from control rats. Losartan treatment in pulmonary hypertensive rats caused a significant 2-fold increase of ACE activity in the hypertrophied right (p<0.005) but not in the left ventricle. Thus, cardiac ACE activity is not stimulated in rats with monocrotaline-induced right ventricular hypertrophy. Prophylactic losartan treatment in this model of progressive pulmonary hypertension failed to prevent or reduce the increase in ventricular afterload. The relevance of the increase in right ventricular ACE activity during pulmonary hypertension after losartan treatment is unknown and needs to be evaluated in further studies.     

血管紧张素转换酶2研究进展

血管紧张素转换酶2是一种金属钛酶,它将血管紧张素I、血管紧张素Ⅱ分别水解为血管紧张素（1～9）及具有血管舒张、抗增殖的血管紧张素（1～7）。血管紧张素转换酶2参与了肾素-血管紧张素-醛固酮系统中多种肽的代谢过程,与高血压、肾脏疾病、糖尿病等发生相关,对心脏、肾脏有一定保护作用,进一步研究其参与保护的机制,有可能为心血管病治疗提供新的靶点。     

Angiotensin Converting Enzyme Inhibitor Therapy and Acute Pancreatitis

Angiotensin converting enzyme (ACE) inhibitors are generally well tolerated. Worldwide, only few reports have been published associating pancreatitis with ACE inhibitor therapy. We report a case in whom there was no other likely explanation for the acute pancreatitis than enalapril therapy, which was temporally associated with the symptoms. Possible mechanisms underlying the induction of pancreatitis by ACE inhibitors are discussed. With the increasing use of ACE inhibitors, the incidence of rare adverse effects such as potentially lethal pancreatitis is likely to increase. Clinicians need to be aware of this association.     

Pharmacological Demonstration of the Additive Effects of Angiotensin-Converting Enzyme Inhibition and Angiotensin II Antagonism in Sodium Depleted Healthy Subjects

A blockade of the hemodynamic and tissue effects of angiotensin II (Ang II) more complete than that presently achieved with usual daily doses of angiotensin converting enzyme (ACE) inhibitors or type 1 Ang II receptor antagonists has potential advantages and risks. Therefore, it is worthwhile to investigate the biological and the hemodynamic effects of the simultaneous blockade of the renin-angiotensin system (RAS) at the two sites where it can be currently achieved, ACE and type 1 Ang II receptors. To investigate this issue, 2 double-blind randomized crossover studies were performed in a model of mild sodium depletion in normotensive volunteers. They ingested single oral doses of captopril 50 mg, losartan 50 mg, their combination or matched placebos, and in a second study, single oral doses of enalapril 10 mg, enalapril 20 mg and the combination of losartan 50 mg with enalapril 10 mg. The combination captopril 50 mg and losartan 50 mg had additive effects on blood pressure fall and renin release in sodium-depleted normotensive subjects. When compared to enalapril 10 mg and the doubling of its dose, the combination of losartan 50 mg and enalapril 10 mg significantly increased both the area under the time curve of mean blood pressure fall and plasma active renin levels. It did not further decrease plasma aldosterone levels. The conclusion is that a more complete blockade of the RAS can be achieved by concomitant administration of an type 1 Ang 11 receptor antagonist and an ACE inhibitor.     

Characterization of Angiotensin Converting Enzyme from Different Rat Vascular Beds

The tissue renin angiotensin system may play a role in cardiovascular pathophysiology. Angiotensin converting enzyme in tissues is now a target for pharmacological inhibition. It is therefore important to determine whether ACE is evenly distributed throughout the vascular tree and whether the enzyme has the same characteristics in different vascular beds. We have thus measured angiotensin converting enzyme density in three functionally different vascular beds with three different methods: the enzyme kinetic assay, a radioligand binding assay and in vitro autoradiography. All three methods demonstrated a significantly higher binding density and activity of ACE in resistance arteries from the mesenteric vascular bed of rats than in microvessels from the brain, or in a conduit artery, the aorta. The dissociation constant (K_d) of the enzyme-radioligand complex was the same in the three functionally different vessel types. Radioligand displacement studies for ACE from plasma and the mesenteric vessels in vitro utilizing a panel of different ACE inhibitors have shown a similar rank order of inhibitory potency suggesting that catalytic sites of ACE were the same in plasma and the mesenteric microvessels. In vivo, the enzyme inhibition in plasma, mesenteric and brain vessels measured by enzyme kinetic and radioligand binding assay were well correlated. There was a similar degree of inhibition between different vessels and tissues (mesenteric vessels, aorta, kidney, left ventricle and coronaries) measured by in vitro autoradiography.     

血管紧张素转换酶基因多态性与原发性高血压之间的关系

目的探讨中国人群中血管紧张素转换酶基因（ＡＣＥ）多态性与原发性高血压之间的关系。方法应用多聚酶链（ＰＣＲ）技术检测ＡＣＥ基因１６含子中２８７ｂｐＤＮＡ片段的插入／缺失（Ｉ／Ｄ）多态性；对７０例原发性高血压患者与４５例正常对照组之间进行比较。结果在原发性高血压组Ｄ等位基因频率（０．５５）高于正常对照组０．４３，但统计学并无意义，在有高血压家族史患者中，Ｄ等位基因频率０．５８高于对照组（Ｐ＜０．０５）。结论，表明在有家族史人群中ＡＣＥ基因多态性与原发性高血压具有相关性。     

Thyroid Hormones Affect Serum Angiotensin I Converting Enzyme Levels

ABSTRACT Serum angiotensin I converting enzyme (ACE) was measured in 10 patients with Graves' disease and 2 with thyroiditis during different stages of the diseases. The effect of thyroxine on serum ACE levels was also recorded in 12 patients with thyroid cancer, who were on thyroxine suppression. Serum ACE levels correlated positively with clinically assessed thyroid function and peripheral thyroid hormone levels, especially during hyper-or hypofunction. ACE was measured both with an enzyme kinetic and a new, quantitative inhibitor binding assay. The methods gave similar results, which indicates that ACE increments during thyroid hyperfunction were quantitative, and not a result of increased enzyme activity. Serum ACE increments associated with high lysozyme concentrations are signs of immunologic activation or proliferation of monocytic cells. In this study there was no correlation between the two enzymes, which may indicate either increased synthesis or possibly shedding of ACE from endothelial cells or delayed metabolic clearance of this enzyme. Serum ACE measurements may provide a useful tool for assessing thyroid function and the effect of thyroxine treatment.     

转换酶抑制剂、血管紧张素受体阻滞剂与心房颤动

心房颤动(Af)为最常见的心律失常,常与心血管发病率和死亡率相关,Af常常需要触发机制诱发及有利的电生理或解剖底物维持,近年对触发Af底物发展这一新的治疗策略产生了兴趣,基础和临床试验资料提示调节肾素-血管紧张素-醛固酮系统(RAAS)或许可减少心脏重塑和Af,现对RAAS抑制剂治疗和预防Af的机制、基础和临床研究结果以及正在进行的临床研究等进行简要综述。     

Angiotensin Converting Enzyme Gene Polymorphism in Turkish Asthmatic Patients

Asthma is a chronic inflammatory disease of the airways. Several candidate genes have been identified with a potential role in the pathogenesis of asthma, including the angiotensin converting enzyme (ACE) gene. We aimed to investigate the frequency of an ACE gene polymorphism in Turkish asthmatic patients and to determine its impact on clinical parameters and disease severity. Ninety-seven asthmatic patients (M/F 25/72, mean age 39 ± 13 years) and 96 healthy subjects (M/F 26/70, mean age 38 ± 12 years) were included. At baseline, all participants completed a questionnaire on demographics, symptoms, triggering factors, severity of asthma, and the presence of atopism. Blood samples were obtained from all patients and genomic DNA was isolated.

The frequency of the ACE genotypes (I = insertion and D = deletion) among asthmatics and controls were compared: asthmatics showed a 40.2% prevalence of the DD genotype (n = 39), ID was 45.4% (n = 44), and II was 14.4% (n = 14.4). In the control subjects, the frequency of DD was18.8% (n = 18), ID was 50% (n = 48) and II was 31.3% (n = 30). The DD ACEgenotype was significantly more frequent in asthmatics compared with controls (p < 0.001). Asthmatics with the ID ACE genotype showed a higher frequency of drug allergies, although this was not statistically significant (p = 0.08). Asthmatics with the DD genotype appeared to have a higher incidence of asthmatic episode exacerbations due to viral infections, but again this was not statistically significant (p = 0.08). Patients with mild or moderate-severe asthma had similar frequencies of these mutations.

We found a higher frequency of the ACE DD gene mutation in Turkish asthmatic patients compared with non-asthmatics, suggesting that this ACE gene polymorphism may be a risk factor for asthma but does not increase the severity of the disease.     

Lack of Association of Angiotensin Converting Enzyme Gene Polymorphism or Serum Enzyme Activity With Coronary Artery Disease in Japanese Subjects

The association of an insertion/deletion (I/D) polymorphism in the angiotensin converting enzyme (ACE) gene or the serum activity of ACE with coronary artery disease (CAD) was investigated in Japanese men and women. The ACE genotype of 947 CAD subjects who underwent coronary angiography and of 893 control subjects was determined by polymerase chain reaction analysis. No association of the DD genotype or the D allele with CAD was observed in men or women. In a low risk group (defined by a body mass index below the median value and the absence of a history of hypertension, diabetes mellitus, and hypercholesterolemia), there was also no association between the ACE gene polymorphism and CAD. No significant difference in serum ACE activity was detected between CAD subjects and controls of all genotypes or of the same genotype, whereas a significant association was apparent between serum ACE activity and ACE genotype for both CAD subjects and controls among both men and women. These results indicate that the ACE I/D polymorphism and genotype associated variation in serum ACE activity are not risk factors for CAD in Japanese men or women.     

Human Angiotensin II Receptors are Regulated By Angiotensin II

Specific angiotensin II (ANG II) binding on human platelets in man was measured to examine ANG II receptor regulation in man. Eight normal volunteers received either a high, or a low sodium diet, or a low sodium diet together with the ANG I converting enzyme inhibitor enalapril. The following parameters were determined at the end of each study period: ANG II platelet receptor binding capacity (B_max) and dissociation constant (K_D); plasma-ANG II, plasma renin, plasma-aldosterone, plasma-atrial natriuretic peptide; and blood pressure (BP) increase to graded doses of i.v. given ANG II. Plasma ANG II (6±0.5, 21±4, 8±1 fmol/ml) and B_max (14±2, 5±1, 10±2 sites/cell) changed in a reciprocal fashion on a high, low or low sodium diet with enalapril respectively. Plasma concentration of atrial natriuretic peptide was unchanged on a low sodium intake and consistently decreased when enalapril was added to the low sodium regimen. BP increase to 4 ng ANG II/kg/min was 27±3, 10±1, and 24±5 mmHg during the three study periods respectively. The data suggest that ANG II regulates maximal capacity of platelet ANG II binding. Therefore, regulation of platelet ANG II binding sites goes in parallel with, and may serve as index for, ANG II receptors on vascular smooth muscle, but ANG II receptor regulation is apparently different in adrenal cells.     

Distribution of Angiotensin Converting Enzyme in Sheep Hypothalamus and Medulla Oblongata Visualized by in Vitro Autoradiography

In vitro autoradiographic mapping of angiotensin converting enzyme (ACE) in sheep brain using the specific ACE inhibitor, ¹²⁵I-351A, revealed very high densities of binding in large blood vessels and choroid plexus. In the forebrain, a very high density of labelling occurred in the organum vasculosum of the lamina terminalis and median eminence and a high density in the subfornical organ and moderate density in supraoptic, suprachiasmatic, arcuate and paraventricular nuclei. All fiber tracts were unlabelled. In the medulla oblongata, a very high density of binding was detected in the area postrema and a high density in the nucleus of the solitary tract and dorsal motor nucleus of the vagus; a moderate density was found in the substantia gelatinosa of the spinal tract and the inferior olivary nucleus.     

血管紧张素转换酶2与高血压

血管紧张素转换酶2与血管紧张素转换酶一样参与肾素-血管紧张素系统中血管紧张素的代谢。它通过将血管紧张素Ⅱ水解成血管紧张素1-7对抗血管紧张素转换酶-血管紧张素Ⅱ代谢轴,是平衡肾素-血管紧张素系统内部调节的另一血管紧张素代谢通路。这种系统的内部调节在调节心血管系统活动中起重要作用,其平衡的破坏与高血压等相关疾病的发生发展密切相关,通过调节血管紧张素2来治疗高血压及其并发症可能是本世纪高血压治疗学上的新靶点。     

Angiotensin II Receptor Antagonist EXP 3174 Reduces Infarct Size Comparable with Enalaprilat and Augments Preconditioning in the Pig Heart

There is no agreement on the effect of angiotensin II receptor blockade in the setting of ischemic reperfusion. Our aim was to assess the acute effects of angiotensin-converting enzyme (ACE) inhibition and angiotensin II AT1-subtype receptor blockade in pig heart. Five groups of open-chest pigs received 1 hour of left anterior descending (LAD) coronary artery occlusion and 2 hours of reperfusion. Left ventricular pressure was monitored by an intraventricular catheter, and regional segment shortening (%SS) in the LAD-supplied territory was measured by ultrasonic crystals implanted in the subendocardium. Group 1 (n = 6) served as the control; groups 2 (n = 6) and 3 (n = 6) received the angiotensin II receptor blocker, EXP 3174 (C₂₂H₂₁Cl₁ N₆O₂), and the ACE inhibitor, enalaprilat, respectively, prior to LAD occlusion; group 4 (n = 6) was preconditioned with two cycles of 10 minutes of coronary occlusion and 30 minutes of reperfusion; and group 5 (n = 6) underwent preconditioning with additional administration of EXP 3174 prior to the 60-minute occlusion period. Infarct sizes were measured by p-nitrobluetetrazolium staining and were expressed in percent of the ischemic area of risk. The angiotensin II receptor blocker EXP 3174 and enalaprilat reduced infarct sizes significantly (35.3 ± 17.1% and 40.1 ± 15.1%, respectively) compared with controls (71.2± 12.8%, P < 0.05), and EXP 3174 augmented the infarct size–limiting effects of preconditioning by ischemia (10.5 ± 6% vs. 28.6 ± 5.3%, P < 0.05). Regional contractile dysfunction during reperfusion demonstrated no changes after angiotensin II receptor blockade. Angiotensin II receptor blockade reduced infarct size comparable with that obtained with angiotensin converting-enzyme inhibition. The infarct size–limiting effects of ischemic preconditioning were augmented by administration of the angiotensin II receptor antagonist EXP3174. These data support the concept that blockade or inhibition of angiotensin II before coronary occlusion is protective in a swine model of acute ischemia and reperfusion. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contribution of Renal Angiotensin Converting Enzyme(ACE) to Blood Pressure Regulation: Possible Role of Brush Border Ace

The role of renal angiotensin converting enzyme(ACE) in blood pressure regulation is not well understood. In our studies, both acute and chronic treatment of hypertensive rats SHR and SHRSP with ACE inhibitors Enalapril and SA446 had a blood pressure lowering effect that coincided with an inhibition of renal cortical and aortic ACE, but not plasma ACE. Further, ACE activities in the renal cortex and aorta were found to increase with aging of the SHRSP, therefore concomitantly with hypertension development. In the kidney, brush border membranes(BBM) contained abundant ACE. We found that the activities of ACE in the renal cortex closely correlated to the activities in isolated BBM, in Wistar Kyoto rats and in the SHRSP. Thus, renal cortical ACE activity and blood pressure correlated in cases of ACE inhibition and hypertension development. Since the ACE activity in the renal cortex appeared to reflect the enzyme activity in BBM, the brush border ACE may have to be taken into account, in view of the relationship between renal ACE, and blood pressure.