摘要:

Objectives:To investigate the regulation of papillary atrial natriuretic factor (ANF) receptors and the differential regulation of glomerular ANF receptor subtypes in one-kidney, one clip (1-K,1C) hypertensionMethods:Plasma immunoreactive ANF levels and atrial and ventricular ANF content were measured in 1-K,1C rats and their normotensive uninephrectomized controls. Glomerular and papillary ANF receptor subtypes were characterized by competitive radioligand binding assay. Stimulation of cyclic CMP (cGMP) production, by increasing ANF doses, was examined in isolated glomeruliResults:Plasma amino-terminal ANF levels were higher in 1-K,1C than in control rats. ANF concentrations in the left atrium were lower and ventricular ANF concentrations were higher in the 1-K,1C group. Competition binding curves for glomerular membranes revealed the presence of two binding sites (ANF-R1 and ANF-R2) in both groups. Total glomerular ANF receptor density was lower in 1-K,1C rats than in their normotensive controls. Both receptor subtypes were downregulated in 1-K,1C rats and their relative proportion was similar to that in glomerular preparations from the controls. ANF-stimulated cGMP production by isolated glomeruli was lower in 1-K,1C than in normotensive rats. In papillary membranes, ANF was bound to a homogeneous population of high-affinity binding sites in both groups. A modest augmentation in the density of papillary ANF receptors was observed in 1-K,1C ratsConclusion:Glomerular and papillary ANF receptors may be regulated differently in the presence of elevated plasma ANF levels. The present results indicate that the downregulation of glomerular ANF-R1 and the reduced cGMP response may lead to altered sodium and water handling by the kidney of 1-K,1C hypertensive rats

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objective:To investigate the effect of the new angiotensin converting enzyme inhibitor ceranapril (1 mg/kg) on the cerebral blood flow (CBF) autoregulation in normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR)Design:Sixteen WKY rats and 16 SHR were given ceranapril 1 mg/ml intravenously and compared with two untreated control groups (n=16). The rats were furthermore divided into subgroups of eight to study the upper and lower limits of autoregulation separatelyMethods:CBF was measured using the intracarotid xenon-133 injection technique. The arterial blood pressure was raised stepwise by noradrenaline or lowered stepwise by controlled bleeding, in order to study CBF over a range of mean arterial pressure (MAP) valuesResults:Baseline MAP was significantly lower in the WKY rat group than in the SHR group. There was no significant difference in baseline CBF between the treated and the untreated groups. Following ceranapril administration, baseline MAP was reduced by lOmmHg in WKY rats and by 20mmHg in SHR, and the limits of CBF autoregulation were reset at lower blood pressure levels. In WKY rats as well as in SHR, ceranapril significantly reduced the lower blood pressure limit of CBF autoregulation. In both strains the upper limit of CBF autoregulation was reduced significantlyConclusion:Ceranapril preserves CBF autoregulation and significantly shifts the limits of CBF autoregulation towards lower blood pressure values.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Aim:To determine the renal, endocrine and haemodynamic effects of an orally active inhibitor of the neutral endopeptidase EC 3.4.24.11 in essential hypertensionMethods:Two groups of 12 white male patients with essential hypertension were treated with candoxatril at 25 mg every 12 h (group 1) or at 200 mg every 12 h (group 2) for 5 days in double-blind, placebo-controlled, crossover studiesResults:Candoxatril enhanced natriuresis over the initial 48 h of treatment. Twenty-fourhour diurnal hormone profiles (day 4) showed modest elevations in plasma atrial natriuretic factor (ANF) concentrations and more clear-cut increases in plasma and urinary cyclic CMP. Plasma angiotensin II and aldosterone concentrations were also significantly increased. Plasma catecholamine concentrations were significantly increased by the higher dose of candoxatril. Blood pressure (day 4, 24-h intra-arterial recordings) fell significantly with both doses. The infusions of exogenous ANF and angiotensin II on day 5 showed that candoxatril impaired the metabolic clearance of both ANF and angiotensin II with consequent enhancement of the biological effects of both effector peptidesConclusions:Candoxatril augments the effects of ANF and lowers blood pressure in patients with hypertension. However, the antihypertensive effects may be offset by increased angiotensin-aldosterone and sympathetic nervous system activity. The blood pressure response to endopeptidase inhibition in hypertensive patients may depend on the relative effects on humoral vasodilator (including ANF) and vasoconstrictor (including the angiotensin-aldosterone and sympathetic) systems

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objectives:To determine whether platelet aggregation to collagen was abnormal in patients with essential hypertension and whether nitric oxide donors and inhibitors of nitric oxide synthesis affect platelet aggregation differently in hypertensives compared with healthy controlsDesign:Platelet aggregation assays were conducted ex vivo from both hypertensive and normal subjects simultaneouslyMethods:Platelet aggregation in response to collagen was measured in platelet-rich plasma from 16 patients with untreated essential hypertension and 16 healthy volunteers matched for age, sex and smoking habits. The effect of sodium nitroprusside (a nitric oxide donor) and NG- monomethyl-L-arginine (L-NMMA), a specific nitric oxide synthase inhibitor, was studiedResults:In healthy controls L-NMMA caused a marked increase in platelet aggregation, whereas in hypertensive patients a small inhibition of aggregation was seen. This was significantly different from the response seen in normal controls. No difference was seen in the aggregatory response to collagen between hypertensive patients and healthy controls. Sodium nitroprusside caused inhibition of aggregation in hypertensive patients and in controls, but there was no significant difference in the degree of inhibition between the two groupsConclusions:We conclude that in platelets from hypertensive patients there is a markedly reduced sensitivity to L-NMMA, which could be explained by a reduction in nitric oxide synthesis

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objectives:To determine whether insulin sensitivity is impaired in normotensive offspring of essential hypertensives and to investigate how it relates to disturbed calcium metabolismDesign:In 10 young lean, normotensive subjects with family histories of essential hypertension and in 10 age-matched controls we investigated insulin sensitivity by the euglycaemic hyperinsulinaemic clamp technique, and 75-g oral glucose tolerance test (GTT). We simultaneously measured calcium-related factors, including the intracellular calcium concentration in platelets.Results:Insulin-induced glucose uptake was significantly impaired in subjects with positive compared with in subjects with negative family history of essential hypertension. Intracellular calcium concentration was significantly higher in subjects with positive than in those with negative family history. Insulin sensitivity was inversely correlated with intracellular calcium concentration (r=—0.56;P<0.05). Those who showed a higher intracellular calcium concentration had impaired insulin sensitivity. Oral GTT results were normal in both groupsConclusion:Impaired insulin sensitivity and disturbed calcium metabolism exist before the onset of hypertension. Insulin sensitivity correlates inversely with intracellular calcium concentration. These findings suggest that the association of the impaired insulin sensitivity and disturbed calcium metabolism may contribute to the development of hypertension

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objectives:To examine the effect of dietary lipid modification on 24-h ambulatory blood pressure, cardiovascular reactivity and sympathetic activity in manDesign:Twenty-four normal volunteers consumed either a high-fat or a low-fat diet for 2 weeks in an open, randomized, crossover study of duration 6 weeks. Diets were isocaloric and balanced for sodium and potassium contentMethods:Cardiovascular reactivity was assessed by measurement of blood pressure responses to incremental infusions of angiotensin II and noradrenaline, and to sympathetic reflex testing. Plasma noradrenaline spillover and clearance rates were estimated using [3H]-noradrenaline infusionResults:Total plasma cholesterol and low-density lipoprotein-cholesterol levels both fell significantly on the low-fat compared with the high-fat diet, as did heart rate and mean arterial pressure (recorded by 24-h ambulatory monitoring). These changes were accompanied by reductions in blood pressure responses to cold pressor testing and to noradrenaline infusion on the low-fat diet. Plasma noradrenaline spillover and clearance rates did not change. Post hoc analysis showed an association between oral contraceptive use and increased noradrenaline sensitivity on the high-fat diet among the females tested.Conclusion:Dietary fat intake alters heart rate, blood pressure and cardiovascular reactivity to noradrenaline in man without changes in basal noradrenaline metabolism.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objectives:First, to determine the relationship between left ventricular mass (LVM) and clinic and 24-h ambulatory blood pressure parameters in normotensive renal transplant recipients. Secondly, to assess the influence of immunosuppression protocol on diurnal blood pressure and target-organ responseDesign:Measurement of supine clinic blood pressure, non-invasive 24-h ambulatory blood pressure and echocardiographically determined LVM.Patients:Twenty-eight stable, normotensive renal transplant recipients taking no antihypertensive therapy (16 cyclosporin-treated and 12 non-cyclosporin-treated). Setting: Community-based ambulatory patients reviewed in tertiary referral centre.Setting:Community-based ambulatory patients reviewed in tertiary referral centreMain outcome measures:Clinic blood pressure, mean 24-h, daytime and night-time ambulatory blood pressure and LVMResults:Mean 24-h blood pressure exceeded that recorded in the clinic. Twenty-five per cent of patients had left ventricular hypertrophy despite the absence of hypertension, and this was more common in cyclosporin-treated than in non-cyclosporin-treated patients. Mean daytime systolic blood pressure was the best predictor of LVM, being superior to clinic blood pressure and any diastolic blood pressure parameter. An attenuated nocturnal blood pressure fall ('non-dipper' pattern) was common, especially in those patients treated with cyclosporin, and was associated with higher LVM.Conclusion:In normotensive renal transplant recipients, a group at risk of cardiovascular disease, 24-h ambulatory blood pressure is closely related to the development of left ventricular hypertrophy, and may prove useful in optimizing treatment strategies to reduce cardiovascular morbidity.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objective:The relationships between blood pressure and the urinary excretion rates of sodium and potassium during the day and at night were investigated. Methods: A total of 160 participants (135 normotensive subjects and 25 untreated patients with essential hypertension) were examined using ambulatory blood pressure monitoring and timed urine collections during waking and sleeping hours.Results:Blood pressure averaged 126/79 mmHg during waking hours and 107/62 mmHg during sleep. More sodium, potassium and aldosterone were excreted during the daytime, but the natriuretic substance kallikrein was excreted at a fixed rate throughout the 24 h. During waking hours there was poor correlation between blood pressure and urinary sodium and potassium excretion. By contrast, at night when the aldosterone: kallikrein ratio fell, the sodium and potassium excretion rates were positively correlated with blood pressureConclusions:Pressure natriuresis, not apparent during waking hours, may be unmasked at night when the balance between sodium-retaining and sodium-losing mechanisms favours natriuresis. Thus, the relationship between blood pressure and 24-h sodium excretion, usually considered to show the influence of salt intake on blood pressure, may also reflect pressure-induced natriuresis, if urine is more completely collected at night than during the day, and in circumstances favouring sodium retention during the day and sodium loss during sleep

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Design:Psychological stress is associated with the development of hypertension. Exercise is purported to have a prophylactic effect on stress. Immediately after a single bout of aerobic exercise there is a transient decrease in blood pressureObjective:We sought to examine the cardiovascular responses to a psychological stressor, the Stroop color word task during the postexercise hypotensive period.Methods:Eight borderline hypertensive subjects (resting blood pressure 137±1.9/ 85 ±1.8 mmHg) participated in three randomly assigned experimental trials: Stroop color word task without prior exercise (Stroop); Stroop color word task administered 10min after 60min exercise at 60% maximal oxygen uptake (Ex + Stroop); and 60min exercise at 60% maximal oxygen uptake followed by 20 min seated recovery (Ex). Blood pressure and heart rate were monitored at the start and end of exercise and at every 2 min of recovery.Results:During the Stroop trial there were significant increases in mean arterial (MAP), systolic (SBP) and diastolic blood pressure (DBP). During the Ex + Stroop trial the increases in MAP, SBP and DBP during the Stroop color word task were significantly less than the increases without prior exercise. During recovery in the Ex trial there were significant decreases in MAP and SBP. However, there were no significant changes in DBP during the Ex trial.Conclusions:These results suggest that following an acute bout of exercise there is a reduction in blood pressure, and during this postexercise hypotensive period the blood pressure response to a psychological stressor is attenuated.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objectives:To determine influence of residence in Israel on blood pressure, glucose, insulin and lipids levels in recent and resident young Ethiopian immigrants, and to compare them with Israeli studentsDesign:Young male Ethiopians, resident in Israel for <3 months and residing in boarding schools, were compared, in a cross-sectional study, with those who had been living under the same conditions for 2 years. The food for both groups was provided from the same kitchen. A group of Israeli students served as an additional comparison groupMethods:Body mass index, triceps skinfold width, sitting blood pressure and fasting glucose insulin, lipids and fructosamine levels were measured and a standard oral glucose tolerance test was performed, with glucose and insulin levels being measured 60 and 120 min after the load.Results:Body mass index did not differ by much between the two Ethiopian groups, but was significantly lower in the Ethiopian groups than in the Israeli student group. Systolic (SBP) and diastolic blood pressure (DBP) were significantly higher in the resident immigrants than in the students, but the high-density lipoprotein-cholesterol, triglycerides, fructosamine and insulin response to oral glucose loading were all significantly lower, whereas the blood glucose response was actually higher. Resident immigrants had a significantly higher prevalence of hypertension. SBP and DBP correlated weakly (r=0.25 and 0.24, respectively) with the sum of insulin after loading among the Ethiopian immigrants but not among the studentsConclusion:After 2 years' residence in Israel, young male Ethiopian immigrants acquire in parallel a rise in blood pressure and an increase in lipidaemia, insulinaemia and glucose response. However, the hypertensive subjects are not hyperinsulinaemic, with increases in insulinaemia accounting for only approximately 6% of blood pressure variability. The increase in the prevalence of hypertension therefore cannot be explained by dietary-induced insulinaemia alone.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID