Blood Pressure in Relation to the Renin—Angiotensin—Aldosterone System

ABSTRACT. The relationship between blood pressure (BP) and the renin—angiotensin—aldosterone system was studied in a stratified random sample (n = 120) of 49-year-old men selected from a BP screening and covering a wide range of BPs. Only subjects not on antihypertensive treatment were included. None had malignant or secondary hypertension. Plasma renin activity, plasma concentrations of angiotensin II, aldosterone, sodium, potassium and noradrenaline and the 24-hour urinary excretions of sodium, cortisol and noradrenaline were determined. Of these variables, only p-aldosterone was significantly correlated with BP, both in the whole study group (R=0.22, p<0.02, n = 119) and in the subjects with the highest BP range (R =0.36, p<0.02, n=30). Of the clinical groups compared, the hypertensive subjects had significantly higher mean p-aldosterone than the borderline and normo-tensive subjects. Multiple regression analysis showed that the 24-hour urinary excretion of noradrenaline was the factor most strongly correlated to p-aldosterone, suggesting that the sympathetic nervous system might stimulate aldosterone secretion. Our findings indicate that aldosterone may be of importance for the development and maintenance of essential hypertension.     

Central Infusion of Aldosterone Increases Blood Pressure by Mechanisms Independent of Na Retention

Experiments were performed to test the hypothesis that Na retention and Na in the diet are not required to initiate central aldosterone induced hypertension. Rats were fed either standard rat chow or Na-deficient diet and infused intracerebroventricularly (i.c.v.) with aldosterone (28 ng/h) dissolved in artificial cerebrospinal fluid (vehicle) or vehicle alone. In Na-replete rats the central infusion of aldosterone did not promote Na or water retention, prior to increases in systolic blood pressure (SBP). Infusion of aldosterone in Na-deficient rats also initiated a rise in SBP, although the response was delayed. In neither group of rats did aldosterone infusion significantly change plasma Na, K, renin, norepinephrine (NE) or vasopressin (AVP) concentrations. There was no significant increase in plasma aldosterone concentration in Na replete rats centrally infused with aldosterone. Infusion of vehicle had no effect on SBP. We conclude that central aldosterone infusion initiates an increase in blood pressure by a mechanism independent of Na retention. Furthermore, increased concentrations of systemic renin, vasopressin, and activation of the sympathetic nervous system do not appear to be involved in maintaining hypertension.     

Renin in the Arterial Wall

Homogenates of rat aortic wall can generate angiotensin I when incubated with nephrectomised rat plasma. This renin-like activity is due to a mixture of proteolytic enzymes. Thus the capacity to generate angiotensin I is greater at pH 5.3 than pH 6.5, although the latter is the pH optimum for rat renal renin. The present work addresses itself to two questions. Is this activity derived from plasma renin? Secondly, does vascular renin-like activity play a role in blood pressure control? Plasma and aortic renin were altered by bilateral nephrectomy and modulation of salt intake. In addition four models of hypertension were studied (early and chronic Goldblatt 2-kidney 1-clip, DOC-salt and spontaneous hypertension). The results indicated that in steady state conditions, aortic and plasma renin-like activity (measured with an incubation pH of 6.5) changed in parallel. When plasma renin was altered acutely however by intravenous injection of renin into nephrectomised rats the half-life of plasma renin was much shorter than the half life of aortic renin. Under these circumstances the pressor response to renin correlated much better with aortic than with plasma renin-like activity. Whilst these studies suggest therefore that renin taken up by the arterial wall is an important determinant of blood pressure, they provide no evidence that accumulation of renin locally produces hypertension in the presence of normal or low plasma renin activity.     

Role of Hypervolemia and Renin in the Blood Pressure Control of Patients with Pyelonephritic Renal Scarring

ABSTRACT Patients with pyelonephritic renal scarring are at risk of developing renal failure and hypertension. We studied glomerular filtration rate (GFR), renal plasma flow (RPF), filtration fraction (FF), systolic (SBP) and diastolic (DBP) blood pressure, fractional sodium, potassium and phosphate excretion, peripheral renin activity (PRA), plasma aldosterone (p-Aldo), urinary albumin excretion (U-Alb) and urinary β₂-microglobulin excretion (β₂-M) in hydropenia and during transition to 3% volume expansion with isotonic saline infusion in 22 female patients with renal scarring due to pyelonephritis and 9 healthy controls. The patients had significantly lower GFR, higher SBP and higher PRA in hydropenia, but there was no significant difference in RPF, FF, DBP or p-Aldo. After volume expansion, SBP, DBP, PRA and p-Aldo were significantly higher in patients than in controls. Transition to 3% volume expansion was associated with a similar increase in SBP in both patients and controls, whereas DBP increased significantly more in the patients (p<0.01). Volume expansion resulted in a significant suppression of PRA and p-Aldo in both patients and controls. The patients with renal scarring had the same capacity to excrete sodium and water during transition to volume expansion as the healthy controls. The renin-aldosterone system seems abnormally activated and is probably more important than hypervolemia in the development of hypertension in this group of patients.     

Insulin Resistance and Blood Pressure Circadian Variation in an Obese Hypertensive Population

Insulin resistance (IR) is related to arterial hypertension and target organ damage. Hypertensive individuals exhibiting a diminished nocturnal blood pressure (BP) reduction (non-dippers) have an increased incidence of cardiovascular events. The association, however, of IR with BP circadian variation has not been evaluated so far. Therefore, this study examined 226 (116 male and 110 female) overweight and obese subjects (BMI > 27kg/m²) with newly diagnosed essential hypertension who underwent clinical and laboratory evaluation, including an oral glucose tolerance test and ambulatory BP measurement (ABPM). IR was estimated using the homeostasis model assessment (HOMA-IR). The population was grouped according to HOMA-IR values > 2.75 (insulin resistance type) or < 2.75 (insulin sensitive type). Results. No significant differences were observed between dippers (n = 137) and non-dippers (n = 89) with respect to age, gender, BMI, serum cholesterol, triglycerides, LDL-C, and HDL-C levels, nor smoking habits. The proportion of IR subjects among dippers (59.1%) and non-dippers (56.7%) was similar (p = 0.833). Moreover, no significant association was found when the HOMA-IR was examined as a continuous component (p = 0.96). Conclusions. Insulin resistance is not associated with nocturnal blood pressure reduction in obese hypertensives. This may be explained by the notion that insulin secretion does not follow a circadian mode of variation.     

Predictive Value of Arterial Blood Pressure in Old Age

ABSTRACT In a 10-year longitudinal study of men and women aged exactly 70 at entry and otherwise only selected according to geography, the predictive value of arterial blood pressure was evaluated concerning cardiovascular disease (CVD) at entry and CVD development or death during the following decade. At 70 the prevalence of arterial hypertension (≤ 160/95 mmHg) was 46% in men and 45% in women. At 80 these prevalences were 19 and 30%, respectively. In women, this fall could partly be explained by an association between high blood pressure and excess mortality. In both sexes it could partly be explained by an increasing part of the population being treated with antihypertensives/diuretics, partly by an association with myocardial degnereration. In a Cox's regression model for competing risks at 70, high systolic blood pressure had independent, predictive value for excess CVD mortality in the eighth decade in women alone, and for excess CVD development in both sexes. High diastolic blood pressure had no independent predicitive value for any of these end points.     

运动血压及其相关影响因素

运动血压即运动试验中的血压,作为高血压研究的重要参数已经引起研究人员的广泛关注。它不仅可以预测正常人群的高血压,而且可对高血压发展及靶器官损害做出评价。现综述运动血压及其影响因素,为高血压的早期预防提供了新思路。     

高血压病人动脉顺应性与家庭偶测血压及动态血压关系

目的　探讨原发性高血压病人家庭测量血压、动态血压与动脉顺应性的关系。方法　共入选 164例受试者 ,其中原发性高血压组 74例 [男 42例 ,女 3 2例 ,平均年龄 ( 4 7 0 5± 10 0 8)岁 ] ;对照组 90例 [男 41例 ,女 49例 ,平均年龄 ( 3 3 81±12 3 5 )岁 ]。对入选者间隔 1～ 3周进行二次家访 ,每次家访由经过专门训练的护士采用汞柱血压计连续测量受试者坐位、左上臂血压 5次 ,每人的家庭测量血压是二次家访、共 10个血压读数的平均值。同时采用SpaceLabs 90 2 0 7动态血压监测仪记录 2 4小时动态血压 ,有效数据应达到 80 %以上。动脉顺应性检查采用动脉脉搏波分析 (PWA)仪。反映大动脉硬化的参数为反射波增强指数 (AIx)。结果　高血压组家庭测量血压及 2 4小时平均收缩压、舒张压、白昼及夜间血压显著高于对照组。与对照组相比 ,高血压组AIx显著升高 ( 2 4 4%± 12 8%vs 12 7%± 18 3 % ,P =0 0 0 0 ) ,经年龄、性别调整后 ,二组间仍有显著性差异 ,提示高血压患者动脉顺应性下降、动脉硬化。将AIx作为因变量 ,年龄、身高、家庭测量血压及动态血压中 2 4小时平均血压、白昼血压、夜间血压、血糖、血酯等作为自变量进行多元回归分析 ,AIx与年龄、家庭血压中的收缩压呈显著的正相关 ,与身高呈负相关     

血浆醛固酮与肾素活性比值在原发性醛固酮增多症筛查中的应用现状及影响因素

血浆醛固酮与肾素活性比值(ARR)是原发性醛固酮增多症(PA)的一个敏感筛查指标,也是评价PA手术预后的指标之一。探讨血浆醛固酮与肾素活性比值测定的影响因素特别是药物、盐负荷和体位的影响对提高ARR的筛查效率具有重要意义。本文就ARR目前的应用情况,测定条件的优化做一介绍。     

The Sodium Intake Modifies the Renin-Aldosterone and Blood Pressure Changes Associated with Moderately Low Energy Diets

ABSTRACT. Thirty middle-aged, moderately obese men with untreated mild hypertension were allocated to two groups of 15 men each. Both groups were placed on energy-reduced diets (5.1 MJ/day) for 9–11 weeks which resulted in similar losses of body mass (8.5 kg). In group I the low energy diet was supplemented with sodium chloride leading to no change in urinary sodium excretion. During dieting there were significant reductions of plasma renin activity (PRA) and urinary excretion of noradrenaline and aldosterone. Heart rate but not mean arterial pressure (MAP) decreased significantly. Then followed a period of sodium restriction which resulted in a significant decrease in MAP and an increase in aldosterone excretion. In group II there was a reduction of sodium intake by about 80 mmol as judged from determinations of urinary sodium excretion. In this group the energy restriction was not accompanied by any changes in PRA or urinary excretion of aldosterone, whereas urinary noradrenaline excretion, heart rate and MAP decreased significantly. Urinary adrenaline excretion remained unchanged. It is concluded that the hypotensive response to moderate energy and sodium reduction cannot be explained by changes in the renin-aldosterone system.     

Effect of Chronic Infusion of Atrial Natriuretic Factor On Plasma and Urinary Aldosterone,Plasma Renin Activity,Blood Pressure and Sodium Excretion in 2-k, 1-c Hypertensive Rats

Conscious two-kidney, one-clip (2-K, 1-C) hypertensive rats and their normotensive sham-operated controls were infused during 13 days with synthetic ANF (Arg 101 Tyr-126) at 35 pmol/hr/rat by means of osmotic minipumps connected to the jugular vein. The initial blood pressure of 186 ± 6 mmHg maximally decreased to 118 ± 7 mmHg at day 5 and slowly rose after wards without reaching basal values. concomitant drop in pressure natriuresis and diuresis was observed. No changes were observed in ANF-infused sham-operated rats. Urinary aldosterone excretion declined in ANF-treated rats from a basal value of 63.38 ± 21.04 μg/24 hr to 13.36 ± 3.78 μg/24 hr the last infusion day. No change in urinary aldosterone was observed in either non-infused 2-K, 1-C or ANF-infused sham-operated rats.

Plasma aldosterone was significantly higher only in non-treated 2-K, 1-C rats. Renal aldosterone clearance was significantly lower in ANF-infused 2-K, 1-C rats than in the other experimental groups. Plasma renin activity (PRA) was lower in treated (3.92 ± 2.26 AI ng/ml/hr) than in non-treated (9.08 ± 2.32 AI ng/ml/hr) hypertensive rats, and not different from ANF-infused or non-infused sham-operated rats. No differences in body weight between infused and non-infused rats, or hematocrit between any group were observed. Atrial immunoreactive ANF was not different in any group. These results demonstrate that chronic administration of ANF not only reduces blood pressure and PRA in 2-K, 1-C hypertensive rats but also plasma and urinary aldosterone. Whether the latter is a direct inhibitory effect or secondary to the normalization of PRA is not known. The hypotensive response may be due to a direct effect on vascular smooth muscle but a role of renin cannot be excluded. Because blood pressure returned toward basal values during the last days of the observation period, the possibility of a tachyphylactic effect of ANF on vascular smooth muscle cannot be excluded     

Practical Aspects of Home and Ambulatory Blood Pressure Monitoring

Out-of-office blood pressure (BP) monitoring is becoming increasingly important in the diagnosis and management of hypertension. Home BP and ambulatory BP monitoring (ABPM) are the two forms of monitoring BP in the out-of-office environment. Home BP monitoring is easy to perform, inexpensive, and engages patients in the care of their hypertension. Although ABPM is expensive and not widely available, it remains the gold standard for diagnosing hypertension. Observational studies show that both home BP and ABPM are stronger predictors of hypertension-related outcomes than office BP monitoring. There are no clinical trials showing their superiority over office BP monitoring in guiding the treatment of hypertension, but the consistency of observational data make a compelling case for their preferential use in clinical practice.     

Aliskiren Reduces Morning Blood Pressure in Hypertensive Patients with Diabetic Nephropathy

Diabetic nephropathy (DN) is a leading disease that requires renal replacement therapy. The progression of renal dysfunction in DN is faster than the other renal diseases. While antihypertensive therapy reduces albuminuria, a good indicator for the progression, hypertension in DN is treatment resistant. Among patients with DN who took angiotensin receptor blockers (ARBs), 27 patients who exhibited poor control of albuminuria were enrolled into the study. Angiotensin receptor blocker was exchanged to aliskiren (150–300 mg/d) and clinical parameters were followed for 6 months. Exchange to aliskiren decreased albuminuria (1.57 ± 0.68 to 0.89 ± 0.45 g/gCr, P < .01) without changes in estimated glomerular filtration rate and office blood pressure (BP). Body weight and hemoglobin A1c were not altered. Aliskiren also reduced plasma renin activity (2.0 ± 0.9 to 1.2 ± 0.6 ng/mL/h, P < .01). While evening BP was unchanged, morning systolic BP (139 ± 8 to 132 ± 7 mm Hg, P < .01) and diastolic BP (81 ± 7 to 76 ± 6 mm Hg, P < .05) were decreased significantly after 6 months. Our results indicated that aliskiren decreased BP, especially morning BP in hypertensive patients with DN. The present data suggest that aliskiren exerts renoprotective actions including reduction in albumin excretion for patients with DN.     

The Genetic Control of Blood Pressure and Body Composition in Rats with Stress-Sensitive Hypertension

The genetic basis of the stress-sensitive arterial hypertension was investigated using the quantitative trait loci (QTL) approach. Two groups of F₂ (inherited stress-induced arterial hypertension [ISIAH] × Wistar albino Glaxo [WAG]) hybrid males of different age (3–4 months old and 6 months old) were tested for blood pressure at rest and stressed conditions and for body composition traits. Several novel loci for the traits were determined. Some loci for blood pressure and organ weight were mapped to the same genetic region in rats of different age. The dynamic change of QTL effects in two rat groups of different age might reflect the process of stress-sensitive hypertension development.     

Blood Pressure Control in Patients with Hypertension: a Community-Based Study

The objective of own study was to investigate the quality of hypertension management in a rural Chinese population. A prospective cross-sectional study was conducted in 922 hypertensive patients in a regional community in southern China. The average systolic (SBP) and diastolic blood pressure (DBP) was 167.8 ± 22.5 mmHg and 94.3 ± 14.2 mmHg respectively. A total of 823 patients (89.3%) patients had a SBP of greater than or equal to 140 mmHg, and 596 (64.6%) had a DBP of greater than or equal to 90 mmHg. Fully 568 patients (69.7%) were treated with one or two antihypertensive drugs, mostly with calcium channel blockers. In patients treated with antihypertensive drugs, the average SBP and DBP were 170.3 ± 23.1 mmHg and 96.2 ± 14.8 mmHg, respectively. Blood pressure was poorly controlled in these hypertensive patients. Further studies are required to identify the barriers to the effective management of uncontrolled hypertension in a rural setting.     

隐性高血压病人中心动脉压及增强指数

目的探讨“隐性高血压”与中心动脉压及动脉硬化的关系。方法采用脉搏波分析仪记录89例临床诊断为血压正常(偶测血压<140/90 mm Hg)及75例高血压(偶测血压≥140/90 mm Hg或正在服用降压药物者)患者的桡动脉脉搏波,经计算机自动转换为相应的中心动脉脉搏波,并分析中心动脉压力及反映全身动脉硬化的增强指数(AIx)。结果小样本人群中,隐性高血压的患病率为15.7%。与血压正常(偶测血压<140/90 mm Hg及白昼动态血压<135/85 mm Hg)组相比,隐性高血压组的血浆总胆固醇及低密度脂蛋白胆固醇浓度、饮酒的比例显著增高;中心动脉收缩压、舒张压、收缩末期压及中心动脉增强压分别增加14.8 mm Hg(CI5.6~24.0 mm Hg)、9.1 mm Hg(CI3.1~15.1 mm Hg)、14.0mm Hg(CI5.8~22.2)及4.2(CI0.6~7.8 mm Hg),增强指数增加11.9%(CI2.8%~20.9%)。虽然隐性高血压组的偶测血压显著低于高血压组,经年龄、性别及身高调整后,两组的白昼动态血压、中心动脉收缩压、舒张压、增强压及增强指数均无显著差异。结论隐性高血压患者的中心动脉压力及增强指数升高,提示动脉顺应性下降,动脉硬化。这些血液动力学的改变可能增加心血管病危险,对其进行评价有助于偶测血压正常者的危险分层。     

Electrocardiogram Blood Pressure and Systolic Time Intervals Long Term Monitoring in Ambulant Patients

Ambulatory monitoring of the intra arterial blood pressure (IBP), through the Selyg-Oxford System, has been used so far primarily for studies on hypertension. Aim of our study is to explore the possibility of obtaining from IBP indications useful to extend its field of application. The study will investigate: 1) the usefulness of the continuous monitoring of the systolic time intervals (STI), measured from IBP as ventricular performance indicators, 2) the increasing of specificity of the ECG allowed by the simultaneous beat by beat estimate of the STI's, 3) the possibility of achieving the same information from non invasive peripheral pressure transducers.

In this paper we are presenting the results obtained from the combined analysis of the STI's, ECG and IBP in a first series of 13 patients, selected out of 50 on the basis of the highest number of episodes of IBP variations, to allow the evaluation of the algorithms performances in severe conditions.