ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Background Structural alterations of large conduit arteries are a common pathway for any complication of hypertensive vascular disease. Whether increased arterial wall thickness occurs at an early phase in uncomplicated hypertension has remained largely ignored until recent years.Methods Sophisticated echo-Doppler techniques with a high degree of resolution and reproducibility have been developed to obtain reliable non-invasive determinations of intima-media thickness of superficial arteries such as the radial and the common carotid arteries.Results In uncomplicated hypertension, a significant increase in intima-media thickness is observed at the sites both of the radial and of the carotid arteries. The former is known to be constantly undamaged by atherosclerosis and is composed almost exclusively of arterial smooth muscle; operational arterial stiffness is found to be normal. The latter is strongly affected by atherosclerosis and predominantly composed of elastin and collagen fibres; operational arterial stiffness is found to be increased. In old subjects with systolic hypertension, radial artery hypertrophy is significantly reversed by drug therapy involving diuretics, converting enzyme inhibitors or both. This change occurs in parallel with the reduction in blood pressure.Conclusion In sustained essential hypertension, arterial wall hypertrophy can be demonstrated in the absence of organ damage. Operational arterial elasticity is maintained in peripheral but not in central arteries. Structural changes of the large conduit arteries are substantially reversed by drug therapy together with a reduction in blood pressure

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo assess the relationships of daytime and night-time blood pressures and the day-night pressure differences, obtained by various analytical methods, with the actual awake and asleep pressures and the awakeasleep pressure difference.MethodsAmbulatory blood pressure was successfully monitored by use of the SpaceLabs 90202 device in 91 healthy young men during a weekend, when they went to bed and awoke at variable and often unusual times. The actual 'awake' and 'asleep' blood pressures were calculated on the basis of these times, noted by the subjects. The 24 h recordings were further analysed by use of two clock time-independent methods (square-wave fitting; cumulative sum analysis) and by one 'wide' (A) and one 'narrow' (B) fixed-time method (daytime: 0700-2200 h or 1000-2000h; night-time: 2200-0700h or 0000-0600 h, for methods A and B, respectively).ResultsIn the total study population, square-wave fitting (+1.1±1.5 mmHg, mean±SD) and cumulative sum analysis (2.4 ±1.9 mmHg) overestimated the actual awake systolic blood pressure and underestimated the asleep pressure (-0.7±1.7 and -1.8±1.8mmHg, respectively). The fixed-time techniques underestimated the awake pressure (-2.6±3.1 and -0.2±3.2mmHg for methods A and B, respectively) and overestimated the asleep pressure by +4.9 ±5.5 and +2.7 ±6.1 mmHg, respectively. The actual awake-asleep pressure difference was overestimated by square-wave fitting (+1.8 ±1.9 mmHg) and more so by cumulative sum analysis (+4.2±2.5mmHg); the underestimation by the fixed time approach averaged -3.0 ±8.4 mmHg with method B and amounted to -7.5 ±8.3 mmHg with method A. Overall, the SD of the various differences between the estimated and the actual awake and asleep pressures, and consequently the limits of agreement, were larger for the fixed-time methods than for the clock time-independent techniques. In the 47 subjects who went to bed before 2400 h and awoke between 0600 and 1000h, the results of the clock time-independent methods were similar to the results in the total study population, whereas the deviations of the fixed time pressures from the actual awake and asleep blood pressures were considerably reduced. The results were similar for diastolic blood pressure.ConclusionsClock time-independent methods, particularly square-wave fitting, can predict the actual awake and asleep blood pressures and the awake-asleep pressure differences with reasonable accuracy and the results are independent of the awake-asleep pattern of the subjects. However, fixed-time methods are only reliable when the subjects go to bed and arise within well-defined periods, and yield more accurate results when the morning and evening phases are excluded from the daytime and nighttime periods

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo compare ambulatory blood pressure recorded during a work day with that recorded during a non-work day.DesignA cross-over randomized study in middle-aged treated hypertensives and normotensives.SettingPrimary health care.SubjectsForty treated hypertensives (20 men) and 40 normotensives (20 men).Main outcome measureIndividual difference between ambulatory blood pressures recorded during a work day and during a non-work day.ResultsThe systolic/diastolic blood pressure of the hypertensives was 2/3 (7/5) [mean (SD)] mmHg higher and that of the normotensives 3/3 (5/4) mmHg higher during the work day 24 h monitoring. The blood pressure of the normotensives showed a statistically significant difference between the two monitoring periods both for systolic and for diastolic blood pressure during 24 h and daytime. The corresponding comparison in the hypertensives showed a significant difference only for diastolic blood pressure. During night-time there was no statistically significant difference between the two monitoring periods, neither in the hypertensives nor in the normotensives. Individual comparisons revealed large variations between the two monitoring periods in many subjects. Among the hypertensives the percentage of subjects with a systolic blood pressure difference>10 mmHg (higher or lower during their work day monitoring period) was 20% during 24 h, 32.5% during daytime and 15% during night-time. The corresponding values for a diastolic blood pressure difference>5 mmHg were 40% during 24 h, 32.5% during daytime and 40% during night-time. Among the normotensives the corresponding values for systolic/ diastolic blood pressure differences between the two monitoring periods were 5/27.5% during 24 h, 5/27.5% during daytime and 2.5/27.5% during night-time.ConclusionAmbulatory blood pressure recorded during a work day might differ from that recorded during a non-work day. It is important to be aware of this fact when evaluating individual blood pressure graphs, although the importance of this for the development of organ damage is not known. To perform more than a single 24 h blood pressure monitoring can be of value to obtain a better idea of the blood pressure variability of a patient

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo investigate the relationship between circulating angiotensin converting enzyme activity and arterial blood pressure in a population-based sample of 646 middle-aged subjects.ResultsAfter exclusion of subjects taking antihypertensive medication and those with electrocardiographic evidence of myocardial infarction, univariate analyses revealed that systolic blood pressure was significantly correlated with age and with body mass index. Also, angiotensin converting enzyme activity in men (n=230) was found to be related both to systolic and to diastolic blood pressure. Inclusion of all of the men slightly strengthened the association between angiotensin converting enzyme activity and systolic or diastolic blood pressure. Multilinear regression models that included age, body mass index and antihypertensive therapy as obligatory covariates confirmed an independent correlation between angiotensin converting enzyme activity and systolic or diastolic blood pressure in the men. Furthermore, untreated men from the highest quartile of angiotensin converting enzyme activity displayed significantly higher mean systolic and diastolic blood pressure values than did those from lower quartiles, even after adjustment for covariates. In contrast, untreated women (n=264) displayed no evidence for such associations between angiotensin converting enzyme activity and blood pressure.ConclusionThe data suggest that the variability of serum angiotensin converting enzyme activity occurring in this large population-based sample might be related to the level of arterial blood pressure levels in men

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo evaluate endothelium-dependent vascular function in obstructive sleep apnoea patients.Design and methodsForearm blood flow and vascular resistance were studied in eight normotensives and eight obstructive sleep apnoea patients and also in eight normotensive and eight hypertensive controls after graded brachial artery infusion of acetylcholine (10-60µg/min) and sodium nitroprusside (1-6µg/min), respectively. Patients and controls were matched for age, sex and body weight.ResultsForearm blood flow after acetylcholine infusion was reduced in patients compared with that in controls (peak flows were 6.0 ±0.7 and 9.8±1.5ml/min for 100g, respectively), but there was no difference between hypertensive and normotensive subjects. However, the hypertensive obstructive sleep apnoea group exhibited a reduced flow response to sodium nitroprusside compared with that of their corresponding hypertensive controls. Minimal forearm vascular resistance after acetylcholine infusion and after sodium nitroprusside infusion was higher in obstructive sleep apnoea patients than it was in controls.ConclusionsEndothelium-dependent vascular relaxation in patients with obstructive sleep apnoea was reduced independently of hypertension. An additional defect in endothelium-independent vascular relaxation was found in obstructive sleep apnoea patients with hypertension. These findings suggest a vascular pathogenetic link between obstructive sleep apnoea and systemic hypertension

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo clarify the significance of C-type natriuretic peptide in the interaction between endothelial cells and vascular smooth muscle cells by investigating the endothelial production of C-type natriuretic peptide and the clearance mechanism of C-type natriuretic peptide using the endothelial cells-smooth muscle cells co-culture system.ResultsSecretion of C-type natriuretic peptide in the direct co-culture of endothelial cells with smooth muscle cells elicited as much as a 60-fold increase compared with endothelial cells alone. The accumulation of intracellular cyclic GMP in the co-culture was consequently increased and the elevation of cyclic GMP level in the co-culture was abolished by the anti-C-type natriuretic peptide monoclonal antibody. The elevated cyclic GMP production in the coculture was abolished by the anti-transforming growth factor-β neutralizing antibody. Candoxatrilat (10-6-10-4mol/l), a neutral endopeptidase inhibitor, dose-dependently increased the concentrations of C-type natriuretic peptide in the culture medium with endothelial cells alone, but not in the endothelial cells-smooth muscle cells coculture. The transcript of neutral endopeptidase messenger RNA was detected in endothelial cells but not in smooth muscle cells by reverse transcriptase polymerase chain reaction. Treatment with C-atrial natriuretic factor4-23(10-9-10-6mol/l), the specific ligand for the clearance receptor of the natriuretic peptides, resulted in dose-dependent augmentation of C-type natriuretic peptide concentration and concomitant intracellular cyclic GMP production in the endothelial cells-smooth muscle cells co-culture but not in endothelial cells alone.ConclusionThe present study demonstrated that direct interaction between endothelial cells and smooth muscle cells augments C-type natriuretic peptide secretion from endothelial cells through transforming growth factor-β activation, and revealed that the enzymatic degradation is responsible for the steady state level of C-type natriuretic peptide in endothelial cells alone and that the receptormediated clearance mainly determines the augmented level of C-type natriuretic peptide in the interaction between endothelial cells and smooth muscle cells. The results taken together raise the possibility that endothelial C-type natriuretic peptide might play a role in regulation of vascular tone and remodelling

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo investigate inositol phosphate formation and its modulation by the cyclic AMP (cAMP) pathway in cultured aortic smooth muscle cells from spontaneously hypertensive rats (SHR).MethodsPhenylephrine was used to stimulate inositol phosphate formation in cultured aortic smooth muscle cells from SHR and Wistar-Kyoto (WKY) rats. The smooth muscle cells from passages 6-14 were prelabelled with myo-[2-3H]-inositol (1.9x105Bq/ml for 24 h) and inositol phosphate formation was measured after exposure to agonist for 45min. (-)lsoproterenol or forskolin-induced cAMP formation was also evaluated using a radioimmunoassay method.ResultsThe basal level of inositol phosphate formation in smooth muscle cells from SHR was higher than that observed in smooth muscle cells from WKY rats. Phenylephrine increased the formation of inositol phosphates in a concentration-dependent manner (0.1-100 μmol/l). In the presence of 100 μmol/l phenylephrine, the increase in inositol phosphate formation was significantly greater in smooth muscle cells from SHR (214±6%) than that observed in smooth muscle cells from WKY rats (156±8%). When the cells were pretreated with 1 mmol/l 8-bromoadenosine 3'5'-cyclic monophosphate or with 10 μmol/l forskolin for 45min, the basal production of inositol phosphates in smooth muscle cells both from SHR and from WKY rats was significantly and similarly decreased by about 20%. In the presence of 1 mmol/l 8-bromoadenosine 3'5'-cyclic monophosphate, 100 μmol/l phenylephrine-induced inositol phosphate formation was similarly decreased by 33±4 and 30±3% in smooth muscle cells from SHR and from WKY rats, respectively, whereas, in the presence of 10 μmol/l forskolin, inositol phosphate formation was reduced by 25±3 and 27±5%, respectively, in those cells. In contrast, isoproterenol induced less inhibition of phenylephrine-induced inositol phosphate formation in smooth muscle cells from SHR (14±2%) than it did in those from WKY rats (25±4.5%). Although there was no significant difference in basal or forskolin-induced cAMP accumulation between smooth muscle cells from SHR and those from WKY rats, (-)isoproterenol-induced cAMP accumulation was significantly lower in smooth muscle cells from SHR.ConclusionA marked inhibitory effect of cAMP on the α1-adrenoceptor-mediated inositol phosphate signal transduction pathway was demonstrated in smooth muscle cells of SHR and of WKY rats. Decreased cAMP formation with ß-adrenergic stimulation and increased inositol phosphate formation with α-adrenergic stimulation in SHR smooth muscle cells may both contribute to the dominant α1-adrenergic activity observed in SHR

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo determine the roles played by kinins/nitric oxide and angiotensin II in the antitrophic effects of angiotensin converting enzyme inhibitors on mesenteric arteries after 3 weeks of streptozotocin diabetes by using blockers both of the angiotensin II AT1receptor and of the bradykinin B2receptorDesignMale diabetic Wistar rats were randomly allocated to receive no treatment, the angiotensin converting enzyme inhibitors perindopril or ramipril, the AT1receptor blocker ZD 7155, the bradykinin B2receptor blocker Hoe 140, the nitric oxide synthase inhibitor NG- nitro-L-arginine-methyl ester, concomitant administration of perindopril plus subcutaneous Hoe 140, perindopril plus A/G-nitro-L-arginine, or ramipril plus Hoe 140 (Hoe 140 administered via an Alzet mini-osmotic pump)MethodsAfter 3 weeks, the rats were killed, their blood collected and their mesenteric vessels removed. The mesenteric vascular weight was measured and the media wall: lumen area ratio was assessed using quantitative histomorphometric techniques. Results Diabetes was associated with an increase in mesenteric weight and media wall: lumen area ratio. The angiotensin converting enzyme inhibitors, perindopril and ramipril, and the AT1receptor antagonist ZD7155 reduced blood pressure and attenuated vascular weight and media wall: lumen area ratio. Concomitant administration of an angiotensin converting enzyme inhibitor with the kinin antagonist Hoe 140, administered either subcutaneously or via a mini-osmotic pump, or of the nitric oxide synthase inhibitor NG- nitro-L-arginine attenuated the effect of the angiotensin converting enzyme inhibitor on the mesenteric vascular weight and wall: lumen area ratios. Treatment with Hoe 140 or NG- nitro-L-arginine alone affected none of these parameters.ConclusionThe antitrophic effect of angiotensin converting enzyme inhibitors on diabetic mesenteric arteries is mediated by inhibition of angiotensin II and by actions on the kinin-nitric oxide pathway

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo determine whether the cutaneous microvasculature of the spontaneously hypertensive rat (SHR) is affected by chronic hypertensionDesignWe used laser Doppler techniques to measure skin blood flow in 22 SHR and in 22 non-hypertensive Wistar- Kyoto (WKY) rats over a 1-year time span, beginning at age 3 months. Sites of measurement included the back, leg, and root of the tail, areas with a predominantly nutritive perfusion, and the plantar surface of the paw, which has a large contribution from large arterioles and venules. Flow was measured at basal skin temperature and at the maximally heat-stimulated condition of 44°C. Systolic tail arterial blood pressures were measured concurrentlyResultAt baseline, systolic blood pressures were considerably higher in the SHR (190±4mmHg) than they were in the WKY rats (138±2mmHg). Skin blood flow values at the three nutritive sites were similar in the two species. However, at 44°C, flow was significantly higher at the paw in the SHR (46.8±3.5 versus 34.3± 2.2 ml/min per 100g). We attribute this difference to the effect of high perfusion pressure on large arterioles. During the 1-year measurement period, there was no appreciable change in blood flow in the WKY rats. In contrast, the SHR showed a steady progressive decline in skin blood flow at all sites. The largest decline was at the paw with a rate of fall of about 2.4%/month. After 1 year, there was no difference between paw blood flow in the SHR (27.5 ±1.8 ml/min per 100g) and in the WKY rats (27.6±1.9ml/min per 100g)ConclusionsSkin blood flow reserve falls in response to chronic hypertension. The rate of fall is greater at sites with significant arteriovenous perfusion than at nutritive sites

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID