ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Whites with essential hypertension have high activity of cell membrane sodium-lithium (Na+-Li+) countertransport when compared with normotensives. To determine whether elevated Na+-Li+countertransport is related to the twofold higher risk of hypertension in US blacks, maximal rates of red blood cell (RBC) Na+-Li+countertransport were measured in 34 black and 21 white male college students. The race groups were similar in social and physical measurements. Mean Na+-Li+countertransport activity (mmol Li/I RBC per h) was significantly lower in blacks than in whites (0.214 ± 0.083 versus 0.295 ± 0.083, P<0.001). Countertransport activity was positively correlated with Type A behaviour among whites (r=0.45, P=0.039). Other within race correlations between Na+-Li+countertransport activity and blood pressure and cardiovascular risk factors were generally positive though not significant in whites, whereas they were small or negative in blacks. If Na+-Li+countertransport has a role in the aetiology of hypertension, it would appear to differ between blacks and whites.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We tested the hypothesis that atrial natriuretic factor (ANF) may play a role in the development of hypertension in salt-sensitive Dahl (S) rats as compared to normotensive salt-resistant Dahl (R) rats. We measured immunoreactive ANF in plasma and atria of the inbred (JR) strain of Dahl S and R rats receiving 0.9 or 8% NaCI diets for up to 8 weeks. We also tested the effect of acute volume expansion on plasma and atrial ANF values in rats receiving the 0.9% salt diet. In addition, we examined the effects of exogenous ANF in the form of atriopeptin III given as intravenous bolus infusion at both levels of salt intake. We found no difference in plasma and atrial values between S and R rats irrespective of salt intake. The S and R rats showed a similar, five- to sevenfold increase of plasma ANF in response to acute saline expansion. Finally, we were unable to demonstrate differences between S and R rats in response to atriopeptin III with respect to transient decreases in blood pressure, and pronounced increases in glomerular filtration rate (GFR), renal blood flow or natriuresis. These results do not reveal appreciable changes in the ANF system of Dahl S rats either before or after onset of hypertension when compared to normotensive R rats. Therefore, our findings do not support the notion that ANF is important in the development or maintenance of chronic salt-induced hypertension in S rats.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Assay of inactive renin in unfractionated mouse plasma is difficult and often impossible because of high concentrations of active renin and plasma protease inhibitors. Therefore, 0.025 to 0.05 ml of plasma or amniotic fluid from mice was separated by high performance liquid chromatography (HPLC) using a silica-based size exclusion column. The eluates were examined for enzymatically active renin before and after limited proteolysis with trypsin. Since inactive renin eluted as a single peak corresponding to a molecular weight of 38 000 daltons and the elution of active renin was markedly retarded, inactive and active renin were partially separated. Compared with plasma, inactive renin in amniotic fluid eluted as a broader and sometimes diphasic peak, suggesting heterogenicity.The rapid and reliable separation by HPLC provided a more than 300-fold purification of inactive renin. Despite low concentrations of plasma protease inhibitors, a 1 000 000- fold molar excess of trypsin (1 mg/ml) was needed for optimal activation. The necessity for high trypsin concentrations for activation may partly be explained by enzyme kinetic considerations.By combining HPLC with trypsin activation, inactive renin was readily measured and found to be 9.4 (5.1-13.2) GU (Goldblatt units)/l in normal and 8.0 (5.1-12.2) GU/I in sialoadenectomized and nephrectomized mouse plasma, which is higher, than previously determined in our laboratory. The concentration was 12.4 (8.8-16.1) GU/I in amniotic fluid. Thus, the concentration of inactive renin in plasma is almost as high as active renin in normal mice (17.6 GU/I) and is uninfluenced by the decrease of active renin to 0.3 GU/I after sialoadenectomy and nephrectomy.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Abnormal sodium(Na+) and water handling by the kidney may be the cause of hypertension in rats of the Milan hypertensive strain (MHS). In addition, the plasma cell membrane Ca-ATPase at Vmax is lower in MHS than in normotensive controls (MNS). The isolated kidney preparation was used to explore the role of extracellular free calcium (Ca2+) concentrations (1.25, 1.00 and 0.75 mmol/l) in tubular Na+transport of pre-hypertensive MHS rats.At the Ca2+concentration of 1.0 mmol/l, the following parameters were significantly higher (P<0.01) in MHS: glomerular filtration rate (GFR) and urinary volume (UV), + 104.8 and +147.2%, respectively; urinary Na+excretion (UNa+), +318.0%; tubular Na+reabsorption (TNa+), +91.0% and oxygen consumption Q O2, +42.9%.Raising the Ca2+concentration to 1.25 mmol/l increased UV (+167.0%) and UNa+( + 231.0%) in MHS without substantially affecting MNS. The difference between the two strains was therefore considerably larger for these parameters, but disappeared for TNa+and Q O2. The overall kidney function of MHS was poor as compared with renal function at Ca2+ 1.0 mmol/l. The differences between the two strains virtually la+ disappeared at the lowest Ca2+concentration (0.75 mmol/l); only GFR and TN. remained slightly greater in MHS mainly because of the poor viability of MNS kidneys in this experimental condition. It thus appears that the lower activity of Ca2+-ATPase of MHS compared with MNS plasma cell membranes influences the differences in Na+and water handling in the two strains.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The mechanism of the hypotensive response to the intravenous administration of atriopeptin III was investigated in rats of the Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) Okamoto strains. Cardiac performance and the systemic haemodynamic response to acute volume loading were evaluated before and during atriopeptin infusion. Cardiac output was measured by a thermo-dilution technique in conscious rats, and left ventricular pressures with differential (dP/dt) calculations were obtained in anaesthetized animals. Bolus injections followed by a 1-h continuous infusion of atriopeptin caused a progressive decrease in mean arterial pressure (MAP) and cardiac output with no significant change in heart rate. In addition there was a transient decrease, maximal at 5 min, and a subsequent increase in peripheral resistance. Atriopeptin did not alter the maximal cardiac output achieved following acute volume expansion. In the anaesthetized animals, bolus injection with a subsequent 15-min continuous infusion of atriopeptin III significantly reduced left ventricular pressures, dP/dt and mean arterial pressure. Volume expansion fully restored intraventricular pressures and dP/dt while increasing mean arterial pressure toward baseline. We conclude that the steady decrease in mean arterial pressure produced by atriopeptin III is due to a decrease in cardiac output secondary to a fall in stroke volume caused by a lowered filling pressure.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Epidemiological evidence indicates that the development of hypertension in human populations depends on the interaction of a genetic heterogeneity and multiple environmental factors. The purpose of this research is to demonstrate the hypothesis that the rise of prevalence of hypertension in developing countries is real and associated with the influence of environmental factors created by the process of 'acculturation'. I have studied all reported prevalence rates of hypertension in Chile between 1936 and 1984. Data from 31 studies in urban and rural populations were correlated to demographic markers of acculturation, life expectancy at birth and urbanization trend (%). Results showed that during this period life expectancy rose from 40 to 67 years and urbanization trend from 51 to 80%. These correlated with the secular increase in the prevalence of hypertension, from a 5% level to almost a 20% level. The study of the cultural breakdown of six rural isolated populations showed after a mean of 15 years a highly significant increase in hypertension prevalence from 1.5 to 7.5%. These positive findings support the hypothesis that the change in prevalence of hypertension in the Chilean population during half a century may be associated with the process of cultural transition to an industrial state

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

In unanaesthetized cats the most striking effects of sino-aortic denervation (SAD) consist of a marked increase in blood pressure variability and a concomitant marked reduction in heart rate variability. Because the relative contribution of carotid and aortic baroreceptors to these phenomena has never been assessed, blood pressure (intra-arterial catheter) and heart rate were measured in unanaesthetized, unrestrained cats for 8-10 h under three conditions: (1) intact animals, (2) 1 week after section of the carotid sinus or the aortic nerves and (3) 1 week after SAD. Blood pressure and heart rate signals were analysed by a computer to provide mean values and variation coefficients of variation i.e. blood pressure and heart rate variabilities, for each recording period. In the intact cats the coefficient of variation was 6.6 + 0.6% (mean ± s.e.) for mean blood pressure and 11.2 ± 1.7% for heart rate. The coefficient of variation for mean blood pressure was not altered by either the aortic or the carotid sinus nerve section, a marked increase being observed only after SAD (11.5 ± 1.3%, P < 0.01). On the other hand, the coefficient of variation for heart rate was reduced either by the carotid or by the aortic nerve section. The reduction observed following the carotid baroreceptor denervation accounted for the greater fraction of the overall reduction (74 versus 26%) in coefficient of variation for heart rate observed after SAD (4.8 ±0.9%, P< 0.01). These data show that (1) the carotid sinus and aortic nerves are similarly involved in control of blood pressure variability, (2) the carotid sinus predominates over the aortic nerves in control of heart rate variability and (3) whereas either the carotid or the aortic baroreceptor area provides a full reflex buffering action on blood pressure variability (whose control mechanisms are redundant), this is not the case for heart rate variability. This control depends on integrity of both reflexogenic areas and, in particular, on the carotid baroreceptors.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Total mortality and cardiovascular disease (CVD) mortality and morbidity during 10 years of follow-up in relation to systolic blood pressure (SBP) at entry were compared between a random sample of 7455 men, aged 47-54 years at entry, in whom multifactorial risk-factor intervention including intense efforts to detect and treat hypertension had been performed [the Primary Prevention Trial (PPT)], and a similar population (from an observational study) in which intervention on CVD risk factors was kept to a minimum (the Study of Men Born in 1913). Total mortality, CVD mortality, coronary heart disease (CHD) and stroke incidence increased with SBP in both populations, but levelled off above the cut-off point for antihypertensive treatment in the population subjected to multifactorial CVD risk factor intervention. In this population total mortality was reduced by 30%, CVD mortality by 37%, CHD morbidity by 13% and stroke morbidity by 30% above the cut-off point for blood pressure intervention compared with the incidence predicted from the observational study. These findings indicate that multifactorial intervention, and especially antihypertensive treatment, have preventive effects in the hypertensive part of the middle-aged male population.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Eighteen unselected patients With untreated mild to moderate essential hypertension, whose average supine blood pressure after 2 months' observation on no treatment was 154/103 mmHg, were entered into a double-blind randomized crossover study of 1 month's treatment with calcium lactate gluconate (40 mmol of elemental calcium/day) and treatment with placebo for a further month. Despite a significant increase in total plasma calcium (P<0.01) and in 24-h urinary excretion of calcium (P<0.025) while taking calcium lactate gluconate, there was no fall in blood pressure with calcium supplementation compared to treatment with placebo.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID