ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Although the concept of the pressure–natriuresis curve is very clear, considerable confusion concerning its importance and utility in understanding the pathophysiology of hypertension persists. We recently showed that the pressure–natriuresis curve could be considered linear. In this brief review, we would like to stress the advantages of treating it as a line. Its linear approximation simplifies understanding of the sodium sensitivity of the blood pressure and mechanisms of hypertension. The blood pressure can be expressed as the sum of two components: the non-sodium-sensitive component determined by the x intercept of the pressure–natriuresis curve and the sodium sensitive one determined by the product of the reciprocal of the slope and the amount of sodium intake. Theoretically, it can be affected in two different ways to cause hypertension; either a parallel shift along the blood pressure axis toward a higher blood pressure level due to the increase in the x intercept or a decrease in the slope. The parallel shift induces non-sodium-sensitive hypertension, whereas the decrease in slope induces sodium-sensitive hypertension. Thus, the linear approximation makes the definition of the sodium sensitivity of the blood pressure very clear and, furthermore, suggests that mechanisms of hypertension can be clarified if the determinants of the x intercept and the slope of the pressure–natriuresis curve are known. A clear definition of sodium sensitivity allows us to study its importance as a marker of a greater risk of renal and cardiovascular complications.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo assess whether the blood pressure is higher among women who take oral contraceptives than it is among those who do not.DesignA cross-sectional survey of a stratified random sample of English adults (aged ≥ 16 years).SettingNon-institutionalized households in England during 1994.ParticipantsFrom this sociodemographically representative sample of English adults, 3545 premenopausal women, of whom 892 were current users of oral contraceptives, were evaluated.InterventionsAn interviewer-administered questionnaire determined details of menopausal status, use of oral contraceptives and antihypertensive agents and other sociodemographic variables. Measurements of the weight, height and blood pressure (the mean of the last two of three readings taken with a Dinamap 8100 device) were recorded.Main outcome measuresSystolic and diastolic blood pressures adjusted for potential confounders by oral-contraceptive-user status.ResultsMean blood pressures adjusted for age were significantly higher among oral contraceptive users (125/70 mmHg) than they were among non-users (123/68 mmHg,P< 0.001 both for systolic and for diastolic blood pressures). These results remained unchanged after further adjustment for the body mass index, alcohol intake, physical activity and hypertension treatment. Blood pressure differences tended to be larger among older oral contraceptive users. Oral contraceptives containing progestogen only were not associated with higher blood pressures.ConclusionsDespite the fact that most combined oral contraceptives in current use in England contain low doses of oestrogen, slightly but significantly higher blood pressures were observed among oral contraceptive users. Blood pressures should be screened before oral contraceptives are supplied and should be monitored regularly during oral contraceptive use.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectivesTo study the relation between the blood pressure and the neurocognitive function within the full adult age range in a large population sample.DesignA cross-sectional study of 936 healthy adults who were recruited from a register of family practices, stratified for age (24–81 years), sex, and occupational level, who took part in a medical and neurocognitive test program.MethodsThe blood pressure status was studied in relation to five measures of cognitive ability, including verbal memory and speed of information processing. Other vascular risk factors were treated as control variables and included smoking, alcohol intake, body mass index, and body fat distribution. The blood pressure was measured five times using an automatic recording technique (with a Dinamap 8100 device).ResultsAfter adjustment for age, sex, and educational level in a hierarchical regression analysis, we found no unequivocal association between the mean systolic and diastolic blood pressures (or any other studied vascular risk factor) and cognitive test performance both for the whole group and for the subgroup of subjects who were not being administered antihypertensive medication and whose medical history did not include cardiovascular events. Stratified analysis within four age levels revealed no age-specific associations between the blood pressure and the cognitive function. Subjects whose blood pressure was within the hypertensive range performed worse than did matched controls at letter digit copying, but not according to other cognitive measures.ConclusionsWith a population-based sample unselected for blood pressure status we found no linear relationship between the actual blood pressure level and various aspects of cognitive performance. Prospective studies are needed to investigate the possibility that the systemic blood pressure load over time is associated with a decline in specific cognitive abilities.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundIt has been suggested that panic disorder can cause or contribute to hypertension or resistance to antihypertensive drugs.ObjectiveTo compare the prevalences of panic disorder, panic attacks, anxiety and depression between patients with resistant hypertension and age- and sex-matched patients with non-resistant hypertension.DesignA case–control study of patients attending the Sheffield Hypertension Clinic, using self-completed postal questionnaires to assess panic disorder, anxiety and depression.PatientsCases with resistant hypertension were defined as patients who presently or previously had systolic blood pressure above 160 mmHg or diastolic blood pressure above 90 mmHg despite the use of three or more antihypertensive agents at full dose. For each of 136 cases, one control with non-resistant hypertension, defined as controlled to ≤ 160/90 mmHg by one or two antihypertensive agents, was identified by a bias-free method. Cases and controls were matched for age and sex.Main outcome measuresLifetime and current prevalence of panic attacks, the prevalences of panic disorder, anxiety and depression by Hospital Anxiety and Depression Scale scores, and the severity and frequency of panic attacks.ResultsOf the resistant hypertensive patients, 33% had experienced a panic attack compared with 39% of the control non-resistant hypertensives (resistant – non-resistant −6%, 95% confidence interval −19 to +7%). Twelve per cent of the resistant patients and 14% of controls fulfilled the criteria for a current or previous diagnosis of panic disorder (resistant – non-resistant −2%, 95% confidence interval −11 to +7%). There were also no significant differences between the groups in the prevalences of current panic attacks, panic attacks rated as moderate or worse, spontaneous panic attacks and in the frequency of panic attacks. There remained no significant difference between the groups for panic attacks and panic disorder when the analysis was limited to those patients who had idiopathic hypertension. The two groups did not differ significantly in scores for anxiety and depression measured by the Hospital Anxiety and Depression Scale.ConclusionWe observed no differences in the prevalences of panic, anxiety and depression between patients with resistant hypertension and non-resistant controls. These factors are probably not implicated in resistance to drug treatment. However, the prevalences of panic disorder and panic attacks were remarkably high in both groups of patients attending a hospital hypertension clinic. The relationship between panic disorder and hypertension deserves further study in a general hypertensive population.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo confirm that westernization of dietary habits represents a stimulus for the expression of cardiovascular risk.DesignThree representative age- and sex-matched samples of general populations of three continents were compared cross-sectionally by analysis of variance.ParticipantsIn total 1110 subjects aged 22–89 years, divided into three groups (370 from Tanzania and Uganda, 370 from the Amazonian region of Brazil, and 370 from northern Italy; 111 men and 259 women in each group).ResultsThe blood pressure of Africans eating a low-salt ‘fish and vegetable’ diet was lower than those of Brazilians, whose diet was based on cereals and meat, and highly urbanized Italians. The systolic blood pressure was correlated to the body mass index for all three populations, but with age only for the Brazilians and Italians. The total cholesterol level and body mass index, both of which are low among Africans, increased progressively with increasing economic level.ConclusionsTransition from a rural to an urbanized lifestyle is accompanied by a rise in the main cardiovascular risk factors; the present data also show that environmental rather than racial factors have a crucial impact on the risk pattern of populations.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo investigate the clinical, biologic, and molecular abnormalities in a family with Liddle's syndrome and analyze the short- and long-term efficacies of amiloride treatment.PatientsThe pedigree consisted of one affected mother and four children, of whom three suffered from earlyonset and moderate-to-severe hypertension.MethodsIn addition to the biochemical and hormonal measurements, genetic analysis of the carboxy terminus of the β subunit of the epithelial sodium channel (βENaC) was conducted through single-strand conformation analysis and direct sequencing. The functional properties of the mutation were analyzed using theXenopusexpression system and compared with one mutation affecting the proline-rich sequence of the βENaC.ResultsMild hypokalemia and suppressed levels of plasma renin and aldosterone were observed in all affected subjects. Administration of 10mg/day amiloride for 2 months normalized the blood pressure and plasma potassium levels of all of the affected subjects, whereas their plasma and urinary aldosterone levels remained surprisingly low. A similar pattern was observed after 11 years of follow-up, but a fivefold increase in plasma aldosterone was observed under treatment with 20mg/day amiloride for 2 weeks. Genetic analysis of the βENaC revealed a deletion of 32 nucleotides that had modified the open reading frame and introduced a stop codon at position 582. Expression of this β579del32 mutant caused a 3.7 ± 0.3-fold increase in the amiloridesensitive sodium current, without modification of the unitary properties of the channel. A similar increase was elicited by one mutation affecting the carboxy terminus of the βENaC.ConclusionsThis new mutation leading to Liddle's syndrome highlights the importance of the carboxy terminus of the βENaC in the activity of the epithelial sodium channel. Small doses of amiloride are able to control the blood pressure on a long-term basis in this monogenic from of hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo investigate the role of the endothelium in the functional interaction between endothelin-1 and norepinephrine in the contractile response of aortas from Wistar–Kyoto (WKY) rats and spontaneously hypertensive rats (SHR).MethodsThoracic aorta rings with and without endothelium from SHR and from WKY rats were suspended in an organ bath to record the isometric tension. After an equilibration period of 120 min, the preparations with and without endothelin-1 were subjected to single and cumulative additions of norepinephrine in different experiments. To characterize the mechanisms involved in the interaction between endothelin-1 and norepinephrine, the aortic rings were pretreated with a cyclooxygenase pathway inhibitor (piroxicam, SQ29548), an inhibitor of NO synthase [NG-nitro-L-arginine (NLA)], or selective endothelin receptor blockers (BQ-123 or BQ-788). In some experiments we examined the contractile responses to norepinephrine in aortas pretreated either with angiotensin II (AII) or with U46619, an agonist of prostaglandin H2–thromboxane A2receptors. Finally, we examined the effect of the combination of calcium-entry blockade by administration of nifedipine and treatment with either endothelin-1 or U46619 on the norepinephrine reactivity.ResultsAdministration of 3 × 10−10mol/l endothelin-1 potentiated the contractile response to norepinephrine in SHR aortas with endothelium, irrespective of whether they had been treated with NLA. No endothelin-1-mediated enhancement of the response to norepinephrine was observed in SHR denuded rings and in untreated and NLA-treated WKY rat aortas. All did not affect the response to norepinephrine in SHR rings with endothelium. The amplification by endothelin-1 of the response to (1–100) × 10−9mol/l norepinephrine was abolished by blockade of the cyclooxygenase pathway with piroxicam or SQ29548. In WKY rat and SHR denuded aortas, 10-8mol/l U46619 potentiated the contractile responses to norepinephrine. Administration of 3 × 10−6mol/l BQ-123 abolished the increase in reactivity to norepinephrine evoked by endothelin-1 in intact SHR aorta, whereas 3 × 10−6mol/l BQ-788 failed to modify this potentiating effect. Administration of 10−8mol/l nifedipine inhibited the potentiation of the norepinephrine-induced contractions evoked both by endothelin-1 in SHR aortic rings with endothelium and by U46619 in SHR denuded rings.ConclusionOur results show that a low concentration of endothelin-1 induced potentiation of the contractile response to norepinephrine in SHR aortas but not in WKY rat aortas. This response was endothelium-dependent. Furthermore, our study affords functional arguments that both endothelial and smooth muscle pathways are involved in the potentiating interaction. We propose that endothelin-1 stimulates the production of endothelium- and cyclooxygenase-generated vasoconstrictor factors, which in turn may serve directly as priming stimuli at the vascular smooth muscle level, to activate the Ca2+-signal pathway and consequently to increase locally the vascular sensitivity to norepinephrine.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo assess the alterations of morphological and functional properties of conductance coronary and mesenteric resistance arteries in spontaneously hypertensive rats (SHR).DesignThe in-vitro intrinsic elastic properties of the wall material in SHR coronary arteries were determined in comparison with those of Wistar–Kyoto (WKY) rats. Mesenteric resistance arteries from rats of both strains were also studied.MethodsArterial segments were cannulated at both ends using an arteriograph system and subjected to pressure increments with simultaneous measurements of the wall thickness and internal diameter. The strain, stress and incremental elastic modulus (Einc) were calculated from diameter–pressure curves.ResultsOver the full range of pressures tested (10–160 mmHg), the internal diameters of SHR coronary arteries were not significantly different from those of WKY rat arteries, whereas we observed that SHR mesenteric resistance arteries had a significantly smaller diameter. The stress-strain curve for coronary arteries was shifted significantly to the left-hand side for the SHR group indicating more stress per unit strain, whereas the opposite was found for mesenteric resistance arteries. When Eincwas determined under isobaric conditions, we found no difference between SHR and WKY rat coronary arteries, whereas this parameter was decreased significantly for SHR mesenteric resistance arteries. When Eincwas estimated at the respective operating pressures, it was 1.7- to 2.8-fold greater for SHR than it was for WKY rat mesenteric resistance and coronary arteries. Moreover, the total collagen area: lumen area ratio was significantly greater for the SHR than it was for the WKY rat coronary artery wall, but this ratio was similar for mesenteric preparations from the two strains.ConclusionThese results show that, at a given stress or operating pressure level, the material of SHR coronary artery wall is characterized by an increase in Einc, whereas there is no increase in Eincfor in mesenteric resistance arteries. This functional alteration is accompanied by an increase in the relative proportion of collagen, a component with a high elastic modulus, in the wall. In contrast, we found no change in elastic modulus and in the relative proportion of collagen for the SHR mesenteric resistance arteries. Furthermore, the present results support the hypothesis that alterations in distensibility differ among the components of the SHR vasculature.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo evaluate the effects of the antisense oligodeoxynucleotide (ODN) to platelet-derived growth factor (PDGF) A-chain messenger RNA (mRNA) on the growth of cardiovascular organs in hypertension.Design15-Mer antisense ODN complementary to the initiation codon region of rat PDGF-A chain mRNA and non-sense ODN of identical proportion but with a random order of bases relative to that of antisense ODN were synthesized with a DNA synthesizer.MethodsWe examined the effects of the antisense ODN on the growth of vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) and Wistar–Kyoto rats, and on the expressions of PDGF A-chain mRNA by reverse transcription and polymerase chain reaction and PDGF A-chain protein by Western blot analysisin vitro. We evaluated the distribution of32P-labeled antisense ODN and examined the effects of the antisense ODN on the growth of cardiovascular organsin vivo.ResultsThe antisense ODN reduced the basal DNA synthesis of VSMC from SHR significantly, but did not do so in cells from Wistar–Kyoto rats. Mutations in the antisense ODN sequence reduced the ODN-induced inhibition of DNA synthesis. Addition of serum or transforming growth factor-β1 increased the DNA synthesis in the SHR-derived VSMC that was inhibited by the antisense ODN. The antisense ODN inhibited the production of PDGF A-chain protein, but not of the PDGF A-chain mRNA. The injection of32P-antisense ODNin vivoled to a greater accumulation of radioactivity in the aorta than in other organs. Infusion of antisense ODN for 28 days did not alter the systolic blood pressure appreciably in rats of either strain. However, in SHR, it reduced markedly the elevated DNA content, [3H]-thymidine uptake, and incorporation of [3H]-thymidine into aortic DNA, and suppressed the production of aortic PDGF A-chain protein. These results indicated that the PDGF A-chain is involved in the exaggerated growth of VSMC from SHR by which inhibition of the translation of PDGF A-chain mRNA to the protein with antisense ODN occursin vitro, and that antisense ODN to PDGF A-chain suppresses the exaggerated arterial proliferation in SHR without alterating the high blood pressurein vivo.ConclusionThese results imply that inhibition of the final responsible growth factor PDGF A-chain by antisense ODN can suppress the arterial proliferation in hypertension without altering the blood pressure, suggesting that the arterial proliferation in hypertension is independent of the high blood pressure in part, and that antisense therapy could be feasible for treating hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID