摘要:

ObjectiveThis editorial was invited by theJournal of Hypertensionas one of a series designed to examine our current knowledge of several aspects of the pathophysiology of hypertension. This article considers small arteries and arterioles.SettingThe conclusion that established hypertension is characterized by a normal cardiac output and a raised peripheral resistance represents the integration of findings from haemodynamic studies using a variety of models of the disease examined by several different techniques. In some ways it assumes that all vascular beds conform to the same pattern of responsiveness. However, given the obvious heterogeneity of functions performed by specialized tissues, the recognized variations in receptor populations and the differences in innervation found in the vascular wall throughout the circulation, this might not be the case. Resistance to blood flow occurs throughout the vascular tree, but the majority is found at the level of arterioles. Upstream small arteries demonstrate growth and remodelling changes which result in luminal narrowing, but the exact contribution of such vessels to resistance is still not known. Perhaps the most interesting recent finding in this context is that blood pressure can fall immediately after a pressor stimulus has been removed, despite the demonstration of such structural changes in small arteries. Furthermore, some whole-animal studies have been reported which fail to show the expected vascular amplification when the circulation is stressed in total.ConclusionViewing the vascular tree as an integrated circuit with specialized functions when nourishing specific tissues suggests that when the resistance in one vascular bed increases because of a constrictor challenge, this might not be representative of the circulation as a whole: indeed, resistance may fall elsewhere. It is probable that structural changes in small arteries represent the consequence of hypertension. The pathogenesis of hypertension may reside downstream in arterioles, where a myogenic response might play a fundamental role.

ISSN:0263-6352    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectivesThe measurement of plasma renin activity (PRA) is very convenient for estimating the action of the renin system, but its interlaboratory reproducibility is notoriously poor. This multicentre study aimed to examine whether an immunoradiometric assay which quantifies renin directly with monoclonal antibodies can reduce this limitation of the enzymatic assay. The study also aimed to establish the reference values of immunoreactive renin (IrR) in a large sample of normotensive subjects and patients with various pathophysiological conditions.Design and methodsPRA and IrR were measured once in each of the eight participant centres in eight pool plasma samples with a wide range of renin content; in seven centres these measurements were repeated twice more in order to compare the intralaboratory interassay reproducibility of both methods. Finally, PRA and IrR were measured in the supine and standing positions in 503 subjects including normal controls, patients with various forms of hypertension, patients with Cushing's and Banter's syndromes, patients with hepatic cirrhosis and pregnant women.ResultsWe found that both the inter- and intralaboratory coefficients of variation for PRA measurements were higher than those for IrR. In plasma samples from normal subjects and from patients, mean±SEM supine PRA and IrR ranged, respectively, from 0.08±0.03 ng/ml per h and 2.6±0.5 pg/ml in patients with Conn's syndrome to 7.2 ±2.5 ng/ml per h and 138±51 pg/ml in patients with hepatic cirrhosis. PRA and IrR were found to be significantly correlated in all laboratories (mean±SEM of correlation coefficients 0.8410.03) and for all of the conditions (correlation coefficient ranging from 0.98 in patients with Cushing's syndrome to 0.50 in pregnant women). However, for the pregnant women the slope of the regression line depicting the PRA-IrR relationship was significantly steeper than for all of the other conditions.ConclusionsIn our experience the inter- and intralaboratory reproducibilities of the immunoradiometric assay appear to be greater than can be achieved with the enzymatic assay, the difference being probably due to the greater complexity of the latter. The two methods provide superimposable information on the renin-angiotensin system activity, except in pregnancy, during which the PRA: IrR ratio is much higher than in the other conditions. Therefore, in this and other pathophysiological situations associated with marked angiotensinogen concentration alterations, the enzymatic assay may be still preferable for assessing the activity of the system accurately.

ISSN:0263-6352    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

The centres participating in the study were: Istituto Patologia Medica I, University of Ancona; Cattedra di Semeiotica e Metodologia Clinica, University of Brescia; Cattedra di Radiologia e Medicina Nucleare, University of Ferrara; Istituto Clinica Medica and Centra Fisiologia Clinica e Ipertensione, University of Milan; Istituto Semeiotica Medica, University of Padua; Istituto Clinica Medica Generate, University of Pisa; Istituto Fisiologia Clinica del CNR, Pisa; and Istituto Clinica Medica, University of Sassari, Italy.

ISSN:0263-6352    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundHypertensives may develop bilateral trapping ofpara-aminohippurate analogues in the tissue of the kidneys during light exercise, as can be demonstrated using radioactively labelled [131l]-hippurate or [99mTc]-mercaptoacetyl-triglycine. Tracer accumulation in the kidneys during exercise results in a typical renographic pattern, the bilateral-abnormal exercise renogram. The disturbance is common during exercise, being found in almost 60% of all hypertensives, regardless of aetiology.ObjectiveTo determine whether bilateral-abnormal exercise renograms are spurious phenomena, or whether the results of exercise renography are reproducible.DesignWe reviewed the renographic examinations of 27 hypertensive patients, each of whom had undergone at least one resting and two [131l]-hippurate or [99mTc]-mercaptoacetyl-triglycine γ-camera exercise renograms. The status of the renal artery at the time of scintigraphy was documented, using available arteriograms. The causes of vascular lesions were noted, as were revascularization procedures and the antihypertensive medication being taken at the time of scintigraphy.ResultsThe average time between exercise renograms was 15.5 months, and 24 of the 27 hypertensive patients had comparable results in the first and the follow-up exercise renogram, divergent results being noted for the other three patients. Re-evaluation of the scintigrams of the three hypertensive patients with divergent results suggested that intermittent pelvic retention might have caused errors of interpretation in two. We found it notable that neither revascularization nor a change in antihypertensive drug therapy influenced the results of exercise renography. Exercise renograms were reproducible over long periods, and potential extraneous influences on blood flow, such as antihypertensive drugs or revascularization, failed to alter the results.ConclusionThe results are considered relevant, because a direct relationship appears probable between hypertension and the disturbance investigated. Reproducible results suggest that the exercise-mediated disturbance is fixed to the kidneys, that it can be reactivated repeatedly and that it may play a role in maintaining hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectiveTo find an objective, sensitive method for quantifying microvascular alterations associated with level of blood pressure and age.DesignA prospective cross-sectional study.Subjects and methodsSeventy-four previously untreated hypertensive patients, referred to a hospital outpatients department, and 26 normotensive volunteers participated. Twenty-four-hour ambulatory blood pressure monitoring and bilateral fundal photography were performed. The fundal photographs were projected on a screen such that the optic disc filled a circle of radius 5 cm. Microvessels crossing the border of a concentric circle of radius 20 cm were identified as arteriolar or venular, counted and their luminal diameters measured.Main outcome measuresArteriolar and venular numbers, mean diameters and vascularities (arteriolar and venular vascularities defined as the sum of arteriolar and venular diameters, respectively).ResultsThe technique was reproducible. As blood pressure increased, arteriolar vascularity declined and venular vascularity increased. These associations resulted in a strong inverse correlation between blood pressure level and the ratio arteriolar vascularity: venular vascularity (r = 0.48,P<0.001). Arteriolar number declined with increasing diastolic blood pressure (r = 0.22,P<0.05). Mean arteriolar diameter appeared to have a U-shaped relationship with diastolic blood pressure levels (r = 0.27,P<0.05). Venular dilation was associated with increasing blood pressure levels (r = 0.22,P<0.05). Mean arteriolar and venular diameters declined significantly with age (r = 0.33 and 0.26, respectively;P<0.01) and there was no association between arteriolar vascularity: venular vascularity ratio and age.ConclusionsThe method detected disparate retinal microvascular alterations with age and blood pressure. The arteriolar vascularity: venular vascularity ratio shows promise as a non-invasive, prognostic and therapeutic guide in hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Objective:To examine the associations between blood pressure and sodium, potassium, calcium and magnesium in a cross-sectional study by 24-h urine collections and food weighing with 3-day food records in 328 males and 335 females in Tianjin, People's Republic of China.ResultsA very high sodium intake and sodium: potassium ratio was confirmed in the study population. After adjusting for confounding variables, both dietary and urinary sodium and sodium: potassium ratio were significantly and positively correlated with blood pressure. Although a negative correlation was found between potassium and blood pressure, the association was significant only between urinary potassium and systolic blood pressure in females and in both sexes combined. No significant associations were found between blood pressure and either intake of or urinary excretion of calcium and magnesium. The dietary intake correlated highly with urinary excretion of electrolytes. In both sexes a strong positive association was found between blood pressure and age, and between blood pressure and body mass index. Higher blood pressure was shown in subjects with higher sodium and alcohol intake, higher body mass index and lower potassium intake.ConclusionThe present results indicate that factors contributing to high blood pressure in Tianjin, People's Republic of China, are related to age, body mass index, high sodium intake and sodium: potassium ratio.

ISSN:0263-6352    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectiveHyperinsulinaemia may be associated with hypertension, hyperlipidaemia and glucose intolerance. In the present study we compared the consequence of immigration from Ethiopia to Israel in order to elucidate environmental effects on these variables.DesignA cross-sectional analysis of 337 young, male Ethiopian immigrants who were placed in boarding schools were divided into two groups: group I was in Israel for <3 months (n = 180) and group II was in Israel for >2 years (n = 157). Both groups were attending the same schools and were fed from the same kitchens.MethodsSitting blood pressure, body mass index, triceps skinfold width, fasting lipids insulin and glucose levels were measured and a standard (75-g) oral glucose-tolerance test was performed.ResultsBoth groups had similar body mass index. Group I was younger than group II. Both systolic and diastolic blood pressure were significantly higher in group II than in group I. Hypertension was more prevalent in group II. Impaired glucose tolerance (from the oral glucose-tolerance test) prevalence did not differ between the groups, neither did the glycosylated haemoglobin nor fructosamine level. The insulinogenic index (ratio of the areas under the curve of the insulin to that of the glucose level during the oral glucose-tolerance test) was significantly higher in group II. Total and high-density lipoprotein-cholesterol levels were significantly higher in group II. In stepped multiple regression analysis, belonging to group II and having higher insulinogenic index predicted hypertension.ConclusionsThis cross-sectional comparison of young, very lean Ethiopian immigrants found those with longer residence in Israel and higher insulinogenic index to have a threefold increase in the prevalence of hypertension in addition to acquiring higher cholesterol levels, indicating that in this ethnically distinct population environmental factors significantly affected the cardiovascular risk.

ISSN:0263-6352    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectiveTo examine whether acute environmental stress (air-jet stress) modulates the exaggerated natriuresis to volume expansion in conscious borderline hypertensive rats.DesignIntravenous isotonic saline volume expansion was performed with and without superimposed acute air-jet stress in conscious borderline hypertensive rats which had consumed a 1% NaCl diet (normotensive) or an 8% NaCl diet (hypertensive) for 12 weeks.MethodsConscious rats were instrumented for measurement of arterial pressure, renal sympathetic nerve activity and collection of bladder urine.ResultsArterial pressure was greater in the 8% NaCI borderline hypertensive rats than in the 1% NaCl borderline hypertensive rats. In the absence of acute air-jet stress the 8% NaCl borderline hypertensive rats exhibited exaggerated natriuresis and exaggerated inhibition of renal sympathetic nerve activity compared with the 1% NaCl borderline hypertensive rats. Acute air-jet stress increased both arterial pressure and renal sympathetic nerve activity reversibly, and attenuated natriuresis in the 8% NaCl but not in the 1% NaCl borderline hypertensive rats.ConclusionAcute environmental stress (air-jet stress) attenuates exaggerated natriuresis in hypertensive but not in normotensive borderline hypertensive rats via increased renal sympathetic nerve activity.

ISSN:0263-6352    

出版商:OVID    

年代:1995

数据来源: OVID