Proliferation of aortic smooth muscle cells and renin-angiotensin system in SHR rats

目的：探讨ＳＨＲ大鼠主动脉平滑肌细胞（ＡＳＭＣ）异常增殖和肾素血管紧张素系统（ＲＡＳ）的关系．方法：测定血管紧张素Ｉ（Ａｎｇ）、卡托普利（Ｃａｐ）、沙拉新（Ｓａｒ）对培养的ＳＨＲ、ＷＫＹＡＳＭＣ增殖和Ａｎｇ、血管紧张素转化酶（ＡＣＥ）的影响．结果：Ａｎｇ在２％血清培养基中可刺激ＳＨＲＡＳＭＣ增生．ＳＨＲＡＳＭＣ分裂增殖能力比ＷＫＹ强，ＳＨＲＡＳＭＣＲＡＳ处于高功能状态．Ｃａｐ长期（４周）干预显著抑制ＳＨＲＡＳＭＣ异常增殖和Ａｎｇ、ＡＣＥ活性，Ｓａｒ长期干预同样抑制ＳＨＲＡＳＭＣ的增殖和ＡＣＥ活性，但Ａｎｇ水平反而升高．Ｃａｐ短期（２４小时）干预不影响两种大鼠ＡＳＭＣＲＡＳ．结论：Ｃａｐ和Ｓａｒ长期干预通过减少ＳＨＲＡＳＭＣＡｎｇ生成或阻断Ａｎｇ和特异受体结合，抑制其异常增殖．     

Effect of captopril on converting enzyme activity in chemically sympathectomized, spontaneously hypertensive rats

Effect of subacute angiotensin converting enzyme (ACE) blockade on the converting enzyme activity (ACE activity) in plasma, aorta, lung, kidney and whole brain was evaluated in chemically-sympathectomized (with 6-hydroxydopamine) normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) using captopril given peripherally via the intraperitoneal (i.p) route and centrally through intracerebroventricular (i.c.v.) administration. Daily i.p. injection of 25 mg/kg for 8 days reduced the blood pressure of both WKY rats and SHR, and the ACE activity in the aorta, lung and plasma of both WKY rats and SHR were correspondingly depressed. The brain ACE activity remained unaltered in both strain of rats. The ACE activity in the kidney of WKY was depressed, while that of SHR remained unchanged. These observations are independent of peripheral sympathectomy with 6-hydroxydopamine (6-OHDA). Daily central captopril administration at a dose of 2 mg/kg, i.c.v., for 8 days significantly reduced the blood pressure of SHR but not WKY rats, whereas the ACE activity of the whole brain of both WKY and SHR were depressed. Central sympathectomy with 6-OHDA did not alter these responses. It is concluded that captopril exerts its antihypertensive effect not only via reduction of the ACE activity in the plasma and lungs as reported earlier, but also that of other organs, principally the aorta, and that these effects are independent of the sympathetic nervous system.     

卡托普利早期治疗自发性高血压大鼠阻止遗传性高血压形成的机理

本文探讨早期卡托普利治疗阻止高血压形成的机制。自发性高血压大鼠（ＳＨＲ）宫内期给药（１００ｍｇ·ｋｇ－１·ｄ－１）到１６周龄，４０ｗｋ处死。测定收缩压，血管壁／腔面积比（Ｍ／Ｌ），血管收缩（后肢灌注Ｆｏｌｋｏｗ模型）和舒张（动脉环体外实验）功能。卡托普利治疗显著降低血压，停药后２４ｗｋ，血压仍维持在相对低的水平（２１．１±１．１ｋＰａ，对照２８．５±１．１ｋＰａ。Ｐ＜０．０１）．治疗能明显减少Ｍ／Ｌ并接近正常ＷＫＹ大鼠水平。治疗组ＳＨＲ大鼠主动脉对硝普钠舒张敏感性及最大舒张反应明显比８ＨＲ增高，后肢阻力血管苯福林灌注显示ＳＨＲ最小灌注压，最大灌注压，曲线最大斜率都明显比ＷＫＹ大，ＥＣ５０明显较小，治疗的ＳＨＲ以上四个指标几乎达到与ＷＫＹ相同水平。结论：卡托普利持久地阻止高血压形成，持久降压的机理可能是在抑制血管肥厚基础上，减弱末梢血管阻力，改善血管舒张功能。关键词     

高血压大鼠学习记忆障碍及降压药物疗效

目的：观察高血压大鼠学习记忆功能的损害并评价比较降压药物的治疗效果。方法：自发性高血压大鼠（ＳＨＲ，１６ｗｋ）分３组（ｎ＝６），其中两组分别使用尼群地平、卡托普利，另一组为对照组；肾血管性高血压Ｗｉｓｔａｒ－Ｋｙｏｔｏ（ＷＫＹ）大鼠（ＲＨＲ，１６ｗｋ）共６组（ｎ＝６），其中５组分别使用卡托普利、美多洛尔、普萘洛尔、硝苯地平、哌唑嗪，另一组不用药。再设一正常对照ＷＫＹ（１６ｗｋ，ｎ＝６）组。治疗８ｗｋ后，连续５ｄ进行跳台试验，每天１０次。结果：两种未经治疗的高血压大鼠ｄ５的主动回避反应计分均有不同程度的下降（ＳＨＲ：０．９±１．１，ＲＨＲ：４．２±１．２ｖｓ，ＷＫＹ：８．７±１．８，Ｐ均＜０．０１）；用药ＳＨＲ两组与对照ＳＨＲ组相比（３．６±１６，４．３±１．８ｖｓ０．９±１．１，Ｐ＜０．０５），记分明显改善；ＲＨＲ美多洛尔７．７±１．６，ＲＨＲ普萘洛尔８．３±１．９，ＲＨＲ卡托普利８．０±２．０，ＲＨＲ硝苯地平７．２±１．７，ＲＨＲ哌唑嗪７．３±１．７，与ＲＨＲ对照（４．２±１．２）比较，Ｐ均＜０．０１；主动回避反应计分有显著提高。进一步比较不同药物治疗组，当降压程度相似时，各组主动回避反应计分无明显差别。?     

Captopril avoids hypertension,the increase in plasma angiotensin II but increases angiotensin 1–7 and angiotensin II‐induced perfusion pressure in isolated kidney in SHR

相似文献   

AUGMENTATION OF ANGIOTENSIN II RELEASE FROM ISOLATED MESENTERIC ARTERIES OF WISTAR-KYOTO AND SPONTANEOUSLY HYPERTENSIVE RATS FOLLOWING NEPHRECTOMY

1. We previously reported that angiotensin II release from the mesenteric arteries of Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) increased in a time-dependent manner as a result of the isolation of the arteries and perfusion. This phenomenon appeared to be due to the withdrawal of circulating angiotensin II (AII). 2. The purpose of the present study was to test the hypothesis that vascular AII generation may be negatively regulated by circulating AII in WKY and SHR, and to clarify the role of this vascular angiotensin II in the sustained hypertension of SHR following nephrectomy. 3. The mesenteric arteries from kidney-intact and nephrectomized WKY and SHR were perfused and the amount of AII released into the perfusate was measured. The effects of the angiotensin converting enzyme inhibitor, captopril, and the effects of supplementation of renal renin and circulating angiotensins to nephrectomized rats, by blood exchange between kidney-intact and nephrectomized rats, on AII release were examined to clarify the pathway of vascular AII generation after nephrectomy. 4. Nephrectomy caused augmentation of vascular AII release both in WKY and SHR in spite of the abolishment of circulating renin. Captopril reduced this enhanced release of AII, but blood exchange did not affect it. There was no significant difference in these responses between WKY and SHR. 5. These results suggest that WKY and SHR have in common a potent pathway for production of vascular AII in response to the withdrawal of circulating AII, although this pathway is not responsible for the sustained hypertension of SHR after nephrectomy. The precise pathophysiological role of this pathway remains to be elucidated.     

阿托伐他汀对自发性高血压大鼠血压和细胞色素P450表氧化酶2C11基因表达的影响

目的研究阿托伐他汀降低自发性高血压大鼠(SHR)血压的作用是否与其调节细胞色素P450表氧化酶2C11(CYP2C11)基因表达的作用有关。方法18只SHR随机分为SHR模型组、阿托伐他汀50和10 mg.kg-1组;6只W istar-Kyoto大鼠(WKY)作为正常对照组。阿托伐他汀ig给药,每日1次,共10周。分别于给药前和给药后每2周测量大鼠尾动脉收缩压(SBP);RT-PCR和W estern印迹法分别检测心、肝、肾及主动脉组织中CYP2C11mRNA和蛋白质表达;ELISA方法检测尿液中14,15二-氢二十碳三烯酸(DHET)含量;并测定血脂含量。结果阿托伐他汀50 mg.kg-1组在给药后第6~10周和10 mg.kg-1组在给药后第10周SBP明显低于SHR模型组。在CYP2C11 mRNA和蛋白质表达中,SHR模型组心、肾和主动脉均明显高于WKY组;给药10周后,阿托伐他汀50 m.gkg-1组的4种组织和10 m.gkg-1组的心、肾和主动脉的表达明显高于SHR模型组。治疗前SHR各组尿液中DHET的含量均显著高于WKY组,给药后阿托伐他汀50 m.gkg-1组的含量明显高于SHR模型组;同时,阿托伐他汀50 mg.kg-1组血脂水平明显低于SHR模型组。结论阿托伐他汀可上调CYP2C11基因的表达,并增加其代谢产物表氧化二十碳三烯酸,这可能是其降低血压的作用机制之一。     

Effects of chronic treatment with captopril (SQ 14,225), an orally active inhibitor of angiotensin I-converting enzyme, in spontaneously hypertensive rats.

The effects of hydralazine (3 mg/kg) and the angiotensin I-converting enzyme (ACE) inhibitor captopril (SQ 14,225) (100 mg/kg) on mean arterial blood pressure, plasma renin activity, urinary volume and urinary Na+,K+, and aldosterone concentrations were examined in spontaneously hypertensive rats of the Okamoto and Aoki strain (SHR) after oral daily dosing for 2 weeks, 3 or 6 months. Captopril caused progressive cumulative reductions in blood pressure resulting in normalization of pressure after 6 months of dosing. Hydralazine also significantly reduced blood pressure but not to the level of normotensive rats of the Wistar-Kyoto strain (WKY). Reductions in heart size paralleled the changes in blood pressure, normalization of cardiac hypertrophy occurring after captopril but not hydralazine. Plasma renin activity increased approximately 2-3 fold after hydralazine and 15-fold after captopril. Neither hydralazine nor captopril had any consistent effects on 24-hr urine volume, urinary Na+,K+ or aldosterone excretion. These results indicate that chronic inhibition of ACE with captopril induces normalization of blood pressure in SHR, a normal-renin model of hypertension.     

Effect of clonidine on renal sodium handling in spontaneously hypertensive rats

Up-regulation of kidney α2-adrenoceptor expression has been implicated in the development of hypertension in spontaneously hypertensive rats (SHR). This study was carried out to evaluate renal sodium excretion in response to clonidine administration in SHR and control normotensive Wistar-Kyoto (WKY) rats. SHR and WKY rats (12-week-old) were placed in metabolic cages for 4 days: the first 2 days in control conditions and the following 2 days under oral clonidine treatment (100 μg/kg body weight). Clonidine produced a similar reduction in systolic blood pressure values in SHR and WKY rats, although SHR remained hypertensive. At the end of the study SHR and WKY rats presented similar noradrenaline plasma levels. However, noradrenaline kidney tissue levels were significantly higher in SHR compared to WKY rats. Under control conditions, SHR presented lower urine flow compared to WKY rats. Clonidine produced a significant decrease in urine flow in WKY rats but not in SHR. Furthermore, clonidine also produced a significant reduction in urinary sodium, potassium, and creatinine excretion in WKY rats, but had no effect in SHR. In conclusion, in SHR the reduction in systolic blood pressure and sympathetic activity produced by clonidine was not accompanied by a decrease in urine volume and sodium excretion.     

Effect of polyphenol-containing azuki bean (Vigna angularis) extract on blood pressure elevation and macrophage infiltration in the heart and kidney of spontaneously hypertensive rats

1. Hypertension is a major risk factor for myocardial infarction and renal damage, and it has also been shown to have pro-inflammatory actions that increase the formation of reactive oxygen species. Macrophage infiltration has been suggested to play a role in the pathogenesis of hypertension. Azuki beans are known to contain pro-anthocyanidins, a group of polyphenolic bioflavonoids with remarkable radical-scavenging activities in vitro. Therefore, the aim of the present study was to investigate the effect of polyphenol-containing azuki bean extract (ABE) on systolic blood pressure (SBP) and macrophage infiltration in the heart and kidney of spontaneously hypertensive rats (SHR). 2. Spontaneously hypertensive rats and control normotensive Wistar-Kyoto (WKY) rats were divided into two groups fed either 0 or 0.8% ABE in their diets. Tail SBP and macrophage kinetics in the heart and kidney were examined. 3. The SBP of the SHR group was higher than that of age-matched WKY rats throughout the treatment period. After 8 weeks of treatment, the increased SBP in ABE-treated SHR was significantly less than that in untreated SHR. 4. Nicotinamide adenine dinucleotide (NADH) or nicotinamide adenine dinucleotide phosphate (NADPH)-stimulated superoxide (O2-) production was enhanced in the kidney and heart in SHR and WKY rats compared with levels in the absence of NADH or NADPH. The NADPH-stimulated superoxide (O2-) levels in the kidney in untreated SHR was significantly higher than that in untreated WKY rats. The (O2-) levels in ABE-treated SHR were significantly decreased compared with the untreated SHR group. 5. In immunohistochemical analyses, the number of macrophages in the heart and in the glomeruli and tubulointerstitium of the kidney was significantly higher in ABE-untreated SHR than in ABE-untreated WKY rats. Conversely, there was a significant decrease in the number of macrophages in ABE-treated SHR compared with the untreated SHR. There were significant positive correlations between SBP and the number of ED1-positive macrophages in the heart and tubulointerstitial and glomerular areas of the kidney in WKY rats and SHR. 6. In conclusion, the results of the present study suggest that ABE attenuates the elevation of SBP and macrophage infiltration in the heart, as well as in the glomeruli and tubulointerstitium of the kidney, in our SHR model.     

自发性高血压大鼠主动脉平滑肌细胞异常增殖和局部肾素—血管？…

目的：探讨ＳＨＲ大鼠主动脉平滑肌细胞（ＡＳＭＣ）异常增殖和肾素－血管紧张素系统９ＲＡＳ）的关系。方法：测定血管紧张素Ⅱ（Ａｎｇ）、卡托普利（Ｃａｐ）、沙拉新（Ｓａｒ）对培养的ＳＨＲ、ＷＫＹ ＡＳＭＣ增殖的Ａｎｇ、血管紧张素转化酶（ＡＣＥ）的影响，结果：Ａｎｇ在２％血清培养基中可刺激ＳＨＲ ＡＳＭＣ增生，ＳＨＲ ＡＳＭＣ分裂增殖能力比ＷＫＹ强，ＳＨＲ ＡＳＭＣ ＲＡＳ处于高功能状态。Ｃａｐ长期（４周     

Differential cardiotoxicity in response to chronic doxorubicin treatment in male spontaneous hypertension-heart failure (SHHF), spontaneously hypertensive (SHR), and Wistar Kyoto (WKY) rats

Life threatening complications from chemotherapy occur frequently in cancer survivors, however little is known about genetic risk factors. We treated male normotensive rats (WKY) and strains with hypertension (SHR) and hypertension with cardiomyopathy (SHHF) with 8 weekly doses of doxorubicin (DOX) followed by 12 weeks of observation to test the hypothesis that genetic cardiovascular disease would worsen delayed cardiotoxicity. Compared with WKY, SHR demonstrated weight loss, decreased systolic blood pressure, increased kidney weights, greater cardiac and renal histopathologic lesions and greater mortality. SHHF showed growth restriction, increased kidney weights and renal histopathology but no effect on systolic blood pressure or mortality. SHHF had less severe cardiac lesions than SHR. We evaluated cardiac soluble epoxide hydrolase (sEH) content and arachidonic acid metabolites after acute DOX exposure as potential mediators of genetic risk. Before DOX, SHHF and SHR had significantly greater cardiac sEH and decreased epoxyeicosatrienoic acid (EET) (4 of 4 isomers in SHHF and 2 of 4 isomers in SHR) than WKY. After DOX, sEH was unchanged in all strains, but SHHF and SHR rats increased EETs to a level similar to WKY. Leukotriene D4 increased after treatment in SHR. Genetic predisposition to heart failure superimposed on genetic hypertension failed to generate greater toxicity compared with hypertension alone. The relative resistance of DOX-treated SHHF males to the cardiotoxic effects of DOX in the delayed phase despite progression of genetic disease was unexpected and a key finding. Strain differences in arachidonic acid metabolism may contribute to variation in response to DOX toxicity.     

几种降压药对自发性高血压大鼠微循环的影响

在自发性高血压大鼠中进行实验，将动物分为三组，分别以氨酰心安，疏甲丙脯氨酸及吲达帕胺治疗。另取一组未经治疗的ＳＨＲ和一组正常血压的ＷＫＹ大鼠作对照。实验１２周后检查，所有降压药治疗的三组ＳＨＲ，血压均降到正常范围；但是睾２肌微循环却显示不高的变化。     

Captopril therapy decreases both expression and function of alpha-adrenoceptors in pre- hypertensive rat aorta

1.-- The effects of captopril on alpha(1)-adrenoceptor mRNA and protein and phenylephrine-induced contraction was assessed in aorta of pre-hypertensive spontaneously hypertensive rats. 2.-- Four-week-old SHR and WKY rats were treated with captopril [an angiotensin-converting enzyme (ACE) inhibitor] 3 mg kg(-1) day(-1) for 1 week. 3.-- pA(2) values for BMY 7378, an alpha(1D)-adrenoceptor antagonist, were 8.63-9.20 among the different groups. Schild slopes were close to unity suggesting that contraction was produced primarily by alpha(1D)-adrenoceptor stimulation and was not changed with therapy. 4.-- Alpha(1D)-adrenoceptor mRNA and protein values were higher in pre-hypertensive SHR than in WKY, whereas alpha(1A)-adrenoceptor mRNA was higher in WKY and alpha(1B)-adrenoceptors were similar in both strains, and protein was not significantly different for alpha(1A)- and alpha(1B)-subtypes. 5.-- Captopril decreased maximal contraction in SHR, without having effect in WKY rats, while alpha(1D)-adrenoceptor mRNA was decreased in both rat strains but alpha(1D)-adrenoceptor protein was significantly decreased only in SHR, and increased alpha(1A)-mRNA in SHR, no effect of captopril treatment was observed on alpha(1B)-adrenoceptor mRNA and protein nor on alpha(1A)-adrenoceptor protein. 6.-- These data suggest that ACE inhibition by captopril influences both expression and function of alpha(1D)-adrenoceptors in aorta of pre-hypertensive rats, probably avoiding alpha(1D)-subtype expression by blockade of angiotensin II synthesis.     

Antihypertensive and hormonal activity of MK 954 in spontaneously hypertensive rats.

MK 954 (DuP 753), a recently developed angiotensin II (Ang II) receptor antagonist, was administered orally for 2 weeks to spontaneously hypertensive (SHR) and Wistar-Kyoto rats (WKY). Whereas the basal levels of plasma Ang II were lower in SHR than in WKY, treatment with MK 954 markedly reduced blood pressure in SHR but not in WKY. Plasma renin activity, Ang I and Ang II were increased, while plasma aldosterone was decreased in both strains. These results no only indicate therapeutic efficacy of this agent in the chronic treatment of human hypertension, but also support the idea that the renin-angiotensin system plays an important role in the control of blood pressure in SHR.     

Chronic antihypertensive treatment with captopril plus hydrochlorothiazide improves aortic distensibility in the spontaneously hypertensive rat.

1. Adult male spontaneously hypertensive rats (SHR) were given captopril plus hydrochlorothiazide mixed in the diet for 10 weeks. Calculated daily doses were 44 mg kg-1 per day for captopril, and 22 mg kg-1 per day for hydrochlorothiazide. Separate groups received captopril or hydrochlorothiazide alone, at similar doses, or no treatment. A final group of WKY normotensive rats received no drug. 2. Systolic arterial blood pressure, measured at regular intervals throughout the 10 weeks' period was lowered but not normalized, in groups receiving either captopril plus hydrochlorothiazide, or captopril alone, but not in the group receiving hydrochlorothiazide alone. 3. Following pentobarbitone anaesthesia, systolic arterial blood pressure, measured in the femoral artery, was found to be lower in all treated groups, but the greatest effect was observed in SHR previously treated with captopril plus hydrochlorothiazide. Aortic pulse wave velocity was also lower in treated SHR, and once again the greatest decrease was observed in the group previously treated with captopril plus hydrochlorothiazide. 4. Following pithing, systolic arterial blood pressures were similar in all SHR groups. Aortic pulse wave velocity was lower in pithed rats previously treated with captopril and hydrochlorothiazide. 5. In conclusion, antihypertensive treatment of SHR produces falls in blood pressure and pulse wave velocity, an indicator of aortic distensibility. Results in pithed rats suggest that treatment with the combination of captopril plus hydrochlorothiazide may increase aortic distensibility independently of blood pressure.     

PLASMA AND PITUITARY PROLACTIN AND BLOOD PRESSURE IN BROMOCRIPTINE-TREATED SPONTANEOUSLY HYPERTENSIVE AND WISTAR-KYOTO RATS

1. The effects on blood pressure (BP) and plasma and pituitary prolactin (PRL) of a 13 day intraperitoneal infusion of bromocriptine delivered by osmotic minipump were investigated in spontaneously hypertensive rats (SHR) and their normotensive controls, the Wistar-Kyoto rats (WKY). 2. In the SHR, a fall in BP which was steepest over the initial few days and sustained up to day 12 was observed in the bromocriptine-treated group compared with the lack of a change in BP observed in the vehicle-treated group. The plasma PRL level taken on day 13 was found to be significantly lower in the bromocriptine-treated group than in the vehicle-treated group. 3. In the WKY, bromocriptine had no significant effect on either BP or plasma PRL. 4. Pituitary PRL content was significantly lower in the SHR than in the WKY. The suppression by bromocriptine treatment was greater in the SHR than in the WKY. 5. These results provide further evidence for a central dopaminergic insufficiency in the SHR and raise the possibility that PRL may, either directly or indirectly by interacting with other factors in the SHR, influence BP.     

Exaggerated pressor response to centrally administered renin in freely moving, spontaneously hypertensive rats

The cardiovascular responses to intracerebroventricular (i.c.v.) injection of renin were compared between freely moving normotensive Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). The i.c.v. injection of renin (0.05-1.0 mU) produced a dose-dependent and a long-lasting rise in mean blood pressure associated with variable changes in heart rate (HR) in both WKY and SHR. However, the blood pressure and HR were not affected by intravenously injected renin (0.1 mU). The pressor response to i.c.v. injected renin was greater in SHR than in WKY, the dose-response curve for renin in SHR being to the left of that in WKY. Central (i.c.v.) pretreatment with [Sar1, Ile8]angiotensin II (50 micrograms) largely abolished the pressor response to i.c.v. injected renin in both WKY and SHR. The i.c.v. injection of angiotensin II (ANG II) (10-100 ng) induced a dose-dependent pressor response which was antagonized by central pretreatment with [Sar1, Ile8]ANG II (50 micrograms). The pressor response to ANG II was also greater in SHR than in WKY. These results suggest that the pressor response to centrally administered renin as well as to ANG II, which is mediated via ANG II receptors located in the brain, is enhanced in SHR.     

HYPOTENSIVE EFFECT OF CHRONICALLY INFUSED ADRENOMEDULLIN IN CONSCIOUS WISTAR-KYOTO AND SPONTANEOUSLY HYPERTENSIVE RATS

1. The hypotensive effect of chronically infused human adrenomedullin (hAM), a potent vasodilator peptide that has been reported to have a natriuretic action, was examined in normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). 2. Conscious WKY rats and SHR were infused with 200 ng/h synthetic hAM for 14 days by means of osmotic minipumps. Control groups were infused at the same schedule with 0.9% saline. Systolic blood pressure (SBP) and daily urinary excretion of Na⁺ and K⁺ were measured before and during the infusion period. In addition, plasma renin activity (PRA), aldosterone and hAM concentrations were measured on day 14 of infusion. 3. A significant reduction in SBP was observed in hAM-treated SHR at day 2 and SBP remained significantly lower throughout the experiment compared with control SHR. Similarly, SBP in the hAM-treated WKY rats was found to be significantly lower than in control WKY rats during infusion. However, the hypotensive effect was not accompanied by any significant increase in urinary volume or Na⁺ excretion in hAM-treated rats of either strain. Chronic infusion with hAM significantly suppressed PRA and lowered the concentration of plasma aldosterone in WKY rats but not in SHR. The plasma hAM levels in treated WKY rats and SHR were 0.0 ± 9.4 and 0.6 ± 0.2 fmol/mL, respectively. 4. These findings demonstrate that chronically infused hAM has a hypotensive effect in both WKY rats and SHR without an increase in urinary volume or Na⁺ excretion at a plasma AM concentration within the physiological limit.     

Effects of captopril (SQ 14, 225) on the renin-angiotensin-aldosterone system in normal rats

High doses of captopril (SQ 14, 225) (120-160 mg/kg/day) were administered orally to normal rats, and the effects on the renin-angiotensin-aldosterone system were observed. Plasma angiotensin converting enzyme (ACE) activity was elevated significantly on the 3rd, 7th and 30th days of captopril administration. ACE activity in the lung and the kidney was significantly decreased on the 1st day then gradually increased, becoming significantly higher than that of controls by the 30th day. Plasma renin activity (PRA) was significantly elevated on the 1st day and remained at a high level until the 30th day. Renal renin content was found to be significantly lower on the 1st and 3rd days. Plasma aldosterone concentration was not affected by captopril treatment, whereas serum potassium concentration was found to be significantly lower on the 1st, 3rd and 30th days. It is suggested that besides its inhibitory action on ACE, captopril has a direct or indirect stimulating action on ACE production as well as on renin release.