摘要:

ObjectiveTo determine whether obese hypertensive patients manifest a diminished regional vasodilator response to an oral glucose challenge.Methods:Nineteen obese hypertensives (body mass index 34.1±1.3 kg/m2, blood pressure 144±3/96±2 mmHg) and 13 lean controls (23.6±0.3 kg/m2, 127±4/83±3 mmHg) were studied. After 1 week on a standard diet, forearm blood flow (plethysmography), systemic hemodynamics (impedance cardiography), glucose and insulin levels were measured at baseline and again at 15, 30, 60, 90 and 120 min during an oral glucose-tolerance test (OGTT).Results:Forearm blood flow increased after the oral glucose ingestion in obese hypertensives and lean controls. The rise in forearm blood flow was greater in obese hypertensives than in lean controls during the 2-h OGTT. Insulin levels also increased more in obese patients after the glucose load. During the second hour of the OGTT the ratio of changes in forearm blood flow and insulin level, an index of vascular insulin resistance, was similar in both groups. In contrast to the regional hemodynamic findings, total systemic vascular resistance decreased in lean controls but did not change in obese hypertensives during the second hour of the OGTT.Conclusion:The forearm vasodilator response to oral glucose in overweight, non-diabetic hypertensives is not impaired. If dynamic increases in flow are indeed important to insulin-mediated glucose disposal, then these observations raise the possibility that the greater increase of regional blood flow during an OGTT in obese hypertensives represents a component of the compensatory response for their defect in glucose metabolism.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background:There is evidence for an altered endothelial function in established hypertension but little is known about endothelial function in borderline hypertension. It has also been suggested that the early stages of hypertension are characterized by an increased sympathetic drive.Objective:To investigate whether alterations in endothelin, neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) are already present in the borderline hypertensive stage.Design:A case-control study of age-matched men recruited from a population screening programme.Methods:Seventy-five men with stable borderline hypertension [diastolic blood pressure (DBP), 85–94 mmHg] and 75 age- and sex-matched normotensive controls (DBP ±80 mmHg) were investigated. Plasma samples were drawn in a standardized fashion, and extracted and analysed using competitive radio immunoassays.Results:Basal concentrations of NPY and CGRP were similar in the two groups (28.4 versus 26.7 pmol/l and 24.2 versus 21.7 pmol/l, respectively). Basal concentrations of endothelin were significantly higher in the borderline hypertensive group (2.0 versus 1.5 pmol/l,P<0.0001).Conclusions:These results suggest that a disturbed endothelial function, represented by endothelin, could be involved in the early hypertensive processes. They also suggest that these changes could be present before the basal sympathetic/parasym-pathetic drive alters, warranting further research into this area.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

ObjectiveTo determine the association between ambulatory blood pressure (ABP) and central hemodynamics in hypertensive patients and between the area under the 24-h blood pressure curve and the hemodynamic indexes.Patient population:Forty untreated essential hypertensive patients (28 previously untreated, 12 withdrawn from therapy for > 12 weeks).Methods:Patients underwent casual and 24-h ABP monitoring and invasive measurements of central hemodynamics. Central measures of ABP included 24-h mean, awake, and sleep values guided by activity journals. The ABP data were modeled by Fourier series and the ability of the smoothed and unsmoothed data to predict hemodynamics was compared. Individual blood pressure curves were analyzed by calculating the area under the curve using different threshold awake and sleep values to test the correlations between this form of blood pressure load and hemodynamics.Results:Hemodynamic measures were not predicted by casual blood pressure but were related to ABP. Total peripheral resistance was strongly predicted by the area under the diastolic blood pressure (DBP) curve using an awake threshold of 90 mmHg and a sleep threshold of 80 mmHg (r = 0.56,P<0.001). Data smoothing using Fourier transformation did not alter any correlations between ABP and hemodynamics. Exercise stroke index, an indicator of cardiac function impaired in early hypertensive heart disease, was also best predicted by area under the DBP curve using the same thresholds as above (r=-0.56,P<0.001).Conclusions:These data imply that integrated areas under the ABP curve are related to hemodynamic hypertensive indexes and could be used to assess the extent of hypertensive burden in clinical trials.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Objectives:Given the reported relationship between systolic hypertension and orthostatic hypotension in the elderly, to test the hypothesis that systolic hypertension causes impairment of the cardiovascular reflex function additional to the effects of age alone.DesignResponses were compared in normotensive healthy young (n = 12) and elderly (n = 15) participants and elderly participants with disproportionate supine systolic hypertension (n = 11) using a baroreceptor-mediated stress (head-up tilt) and two non-baroreceptor-mediated stimuli (cold pressor test and isometric exercise).Methods:Blood pressure and heart rate were measured by oscillometry before and during the three stress tests. Forearm blood flow was measured by venous occlusion plethysmography and pulse wave velocity (PWV) by Doppler ultrasound.Results:Percentage changes in systolic/diastolic (SBP/DBP) blood pressure with head-up tilt were 0/+11, −3/0 and −6/+1 mmHg in the young and elderly normotensives and elderly systolic hypertensives, respectively. Both elderly groups had reduced DBP responses to tilt compared with the young (P<0.01). All three groups had similar percentage changes in blood pressure responses to non-baroreflex-mediated stresses (cold pressor test: +10/+23, +11/+11, +10/+15; sustained isometric exercise: +18/+33, +22/+24, +13/+17 in the young and elderly normotensives and elderly systolic hypertensives, respectively). Aorto-iliac PWV adjusted for blood pressure was significantly higher in both elderly groups compared with the young (P<0.01) but there was no difference between elderly normotensives and hypertensives. Unadjusted PWV was higher in elderly hypertensives than in elderly normotensives (P<0.05).Conclusions:Compared with healthy young participants, both elderly groups had similarly attenuated blood pressure responses to tilt and reduced arterial compliance. Systolic hypertension is not associated with additional impairment of cardiovascular reflex function over and above the effects of age. The reported association between supine systolic hypertension and orthostatic hypotension does not appear to be a causative one.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background:Experience with the original protocols of the Association for the Advancement of Medical Instrumentation (AAMI) and the British Hypertension Society (BHS) for validating blood pressure has provided valuable insight into the methodological problems associated with device validation and has influenced both the BHS and the AAMI in revising their protocols.Objectives:To review the revisions of the original BHS and AAMI protocols; to compare the protocols; and, using the BHS protocol as a framework for validation, to determine how it should be modified to a protocol that will fulfil the criteria of both the AAMI and the BHS.Conclusions:The revised protocols have many similarities but there are some important differences. These differences merit consideration so as to facilitate manufacturers seeking to validate devices for acceptance in both Europe and the United States. Of the two protocols, the BHS protocol is the more elaborate in that (1) it takes particular care to ensure that observers are trained to a very high standard, (2) it makes provision for special group validation and (3) it recommends in-use validation of all devices. By modifying the BHS protocol, it is possible to validate blood pressure measuring devices (ambulatory devices require special consideration) to satisfy the criteria of both protocols.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Objectives:To determine whether Hispanics are at lower risk for the development of hypertension than non-Hispanic Whites. We also examined selected predictors of hypertension incidence and explored the role of markers of insulin resistance in the development of hypertension.DesignA cohort study of a geographically-based sample of Hispanic and non-Hispanic white southern Colorado residents who were re-examined an average of 4 years after their baseline examination.Methods:These analyses included 664 participants who were normotensive and confirmed nondiabetic by an oral glucose tolerance test at their baseline examination. Hypertension was defined as systolic blood pressure ± 140 mmHg or diastolic blood pressure ± 90 mmHg or use of antihypertensive medication.Results:Hispanics and non-Hispanic Whites had similar hypertension incidence rates. The strongest predictors of hypertension incidence were baseline blood pressure and age. Higher baseline heart rates and higher body mass index also predicted hypertension. Increased fasting insulin levels were associated with hypertension incidence among lean participants, though the association disappeared once baseline blood pressure levels were added to the models. Models investigating change in systolic or diastolic blood pressure levels found higher baseline levels of insulin area under the glucose tolerance curve predicted greater increases in systolic blood pressure in non-Hispanic Whites only.Conclusions:Hypertension incidence rates were similar in Hispanics and non-Hispanic Whites. Higher levels of insulin area were associated with larger increases in systolic blood pressure among non-Hispanic Whites only.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Objectives:To compare blood pressures in northern (Beijing) and southern (Guangzhou) Chinese population samples aged 35–54 years, males and females, urban and rural, and to assess the role of blood pressure-related traits in explaining north-south differences.DesignCross-sectional surveys were conducted in 1983–1984 of northern and southern populations employed in industry (urban) or farming (rural).Methods:In the north samples were selected from the Capital Iron and Steel Complex (urban) and Shijingshan district (rural); in the south samples from the Guangzhou Shipyard (urban) and Panyu County (rural) were used.Results:The number of subjects surveyed in north and south were 4706 and 4179, respectively: 1500 and 1052 urban males, and 717 and 914 rural males; and 1300 and 1061 urban females, and 1189 and 1152 rural females, respectively. Average systolic (SBP) and diastolic (DBP) blood pressures, were consistently higher in the north than in the south. SBP and DBP were significantly and independently related to age, body mass index, heart rate, use of antihypertensive drugs, serum triglycerides level, alcohol use (males only) and inversely to cigarette smoking. Northerners were older, taller, heavier and had higher body mass index and triglycerides level than southerners. With adjustment of SBP and DBP for blood pressure-related traits, north-south blood pressure differences decreased, but remained significant for urban males, rural males and rural females, with sizeable differences for rural samples in particular.Conclusions:North-south differences in blood pressure in these samples are accounted for only partly by north-south differences in the cited blood pressure-related traits. The role of other traits requires assessment.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Introduction:Fibronectin is a dimeric glycoprotein found in the extracellular matrix of most tissues. It can influence cell growth, adhesion and migration. Fibronectin synthesis is overexpressed in hypertension. However, the respective effects of humoral factors, including angiotensin II, and mechanical factors in vascular remodelling have not yet been clarified. To study fibronectinde novosynthesis in the arterial wall, we have developed a new model for organ culture of rabbit thoracic aorta.Methods:Arteries held at theirin vivolength were incubated and perfused (40ml/min) in DME medium containing antibiotics, supplemented widt 20% fetal calf serum or 5% bovine serum albumin. In a series of experiments, angiotensin II (10-6mol/l) and indomethacin (10-5mol/l) were added to culture media. Vessels were pressurized at 0, 80 or 150 mmHg, and incubated for 3 days at 37±C under 5% CO2.De novosynthesis of fibronectin was detected by immunofluorescence using anti-cellular fibronectin antibodies (1:200).Results:In the absence of angiotensin II and serum, fibronectin was expressed in the sub-endothelium at 80 mmHg, and in the inner media at 150 mmHg. In the presence of serum, fibronectin expression was increased by the high pressure. When angiotensin II was added, a gradient of fibronectin became apparent in the inner media at 80 mmHg with a marked expression at the luminal side. Angiotensin II markedly enhanced fibronectin expression at 150 mmHg, the protein being detected in almost all of the media.Conclusion: Our results indicate that both angiotensin II and transmural pressure can induce fibronectin expression in the arterial wall, and the two act synergically.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

ObjectiveOur objective was to determine whether the selective angiotensin II type 1 (AT1) receptor antagonist losartan interacts with thromboxane A2/endoperoxide (TXA2/PGH2) receptors.Methods:We measured changes in mean pulmonary arterial pressure (MPAP) induced by the stable TXA2analogue U-46619 during blockade of either TXA2/PGH2or AT1receptors in anesthetized, open-chest rats (four to eight per group).Results:U-46619 (1.25 and 10 μg/kg) dose-dependently increased MPAP. The 1.25 μg/kg dose of U-46619 increased MPAP (±51%,P<0.01), was dose-dependently inhibited by the TXA2/PGH2receptor antagonist SQ 29,548 (±94 and 102% at 0.63 and 2.5 mg/kg, respectively; bothP<0.05). Losartan also dose-dependently reduced this increase (±11 and 65% at 2.5 and 10 mg/kg, respectively;P=NS andP<0.05, respectively). Furthermore, losartan dose-dependently prevented the increase in MPAP (±112%) induced by an eightfold higher dose of U-46619 (10 μg/kg) by ±9 and 75% at doses of 10 and 40 mg/kg, respectively;P=NS andP<0.05, respectively.Conclusions:Thus, selective activation of TXA2/PGH2receptors by the TXA2analogue U-46610 induced pulmonary hypertension, which was specifically inhibited by the TXA2/PGH2receptor antagonist SQ 29,548 and the AT1receptor antagonist losartan, suggesting that the latter exerts antagonist activity at TXA2/PGH2receptors.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

ObjectiveIn this study, we determined (1) whether chronic anti-hypertensive treatment can alter myocardial free intracellular magnesium concentrations, and (2) whether changes in magnesium concentration correlate with resistance to anoxia of hypertensive rat hearts.Methods:Six-month-old male spontaneously hypertensive rats (n=11) were compared with rats from the same strain treated with the calcium-channel antagonist nitrendipine (60mg/kg per day; n=11) or the converting enzyme inhibitor perindopril (2mg/kg per day; n=9) for 3 months. The hearts were perfused in retrograde isovohimic mode and submitted to a standardized anoxia recovery protocol. Aortic perfusion pressure and left ventricular pressure were monitored constantly. P-31 nuclear magnetic resonance (NMR) spectra were simultaneously recorded and allowed to quantify the changes in myocardial inorganic phosphate, phosphocreatine and ATP. The pH was derived from the chemical shins of inorganic phosphate and phosphocreatine, and the free intracelhilar magnesium concentration from the α-β chemical shifts ofATP.Results:Both treatments lowered systolic blood pressure and reversed left ventricular hypertrophy, perindopril being slightly more efficient at the dose administered. Intracellular magnesium concentration, calculated from the P-31 NMR spectra, was 277±17 μmol/l in the untreated hypertensive group, 311 ± 15 μmol/l in the nitrendipine group and 401 ±17 μmol/l in the perindopril group (P< 0.001 versus untreated and nitrendipine). There was a significant correlation between intracellular magnesium concentration and left ventricular developed pressure at the early stage of post-anoxic recovery (r=0.61,P<0.01).Conclusion:P-31 NMR spectroscopy demonstrates an increase in myocardial free intracellular magnesium concentration following chronic administration of the angiotensin converting enzyme inhibitor perindopril to spontaneously hypertensive rats. The increase in free magnesium concentration may contribute to the cardioprotective effect of perindopril.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID