摘要:

Corticotropin releasing factor and vasopressin were measured in major brain regions including the neurohypophysis in spontaneously hypertensive rats (SHR) and normotensive VVistar-Kyoto rats (WKY) during development of hypertension. The highest concentration of corticotropin releasing factor was found hi the hypothalamus in both strains. Corticotropin releasing factor was decreased in most major brain regions of SHR. In the hypothalamus, corticotropin releasing factor was lower in 3-and 6-week-old SHR than in age-matched WKY (p< 0.01), but was similar at 12 and 24 weeks of age. The content of corticotropin releasing factor did not differ in the neurohypophysis in 3-week-old rats but began to decrease at 6 weeks of age (p< 0.01) and continued to decrease during the development of hypertension (p< 0.01). Brain vasopressin concentration did not differ between SHR and WKY except in the hypothalamus. The level of hypothalamic vasopressin was consistently lower in SHR than in WKY (p< 0.01). These peptides are thought to be associated with autonomic nervous regulation, and our results may further strengthen the possibility that the deficit of the peptides may be involved in the development of spontaneous hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The Na+-K+pump activity was determined in femoral arterial smooth muscle from deoxycorticosterone acetate (DOCA)-salt hypertensive rats using potassium relaxation and ouabainsensitive86Rb uptake as indices. The membrane-stabilizing effect of calcium and its relation to Na+-K+pump activity also were examined. Femoral arteries from DOCA-saJt rats exhibited a greater relaxation in response to potassium addition after contraction with norepinephrine in a low potassium (0.6 mM) Krebs solution. The concentration of potassium required to produce a 50% relaxation was significantly less in DOCA-salt rats. Ouabain-sensitive86Rb uptake was significantly greater at 3,10, and 20 minutes of86Rb incubation in femoral arteries from DOCA-salt rats. Linear regression analysis revealed a significant correlation between the uptake of86Rb and time of incubation in both control and DOCA-salt rats. A significant difference in the slopes of the regression lines showed that the rate of uptake was greater in DOCA-salt rats. No difference was observed in ouabain-insensitive86Rb uptake. A dose-dependent relaxation in response to increasing concentrations of calcium following contraction to norepinephrine was observed in femoral arteries from control and DOCA-salt rats. The relaxation was directly dependent on the level of extracellular potassium and was blocked by ouabain. Femoral arteries from DOCA-salt rats relaxed to a significantly greater extent in response to calcium at each level of potassium when compared with controls. These results provide further evidence for an increase in Na+-K+pump activity in vascular smooth muscle from DOCA-salt hypertensive rats. In contrast to previous reports, however, calcium-induced relaxation was shown to be increased in the DOCA-salt rat. This effect is directly dependent on the activity of the Na+-K+pump and supports observations of increased potassium relaxation and86Rb uptake.

ISSN:0194-911X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The effect of angiotensin II (5, 10, and 20 ng/kg/mln) on blood pressure and on the plasma concentrations of aldosterone was studied in six healthy men with and without the concomitant administration of synthetic human atrial natriuretic peptide given 1) as an i.v. bolus of 25 fig followed by a 6-hour infusion of 25 μg/hr or 2) as an i.v. bolus of 175 μg followed by a 6-hour infusion of 100 jig/hr. The pressor effect of angiotensin II (i.e., the rise of mean blood pressure above individual basal levels) remained unchanged during the administration of both doses of human atrial natriuretic peptide. The angiotensin II-induced rise in plasma concentrations of aldosterone (in terms of absolute values) was reduced by human atrial natriuretic peptide during both trials. The rise in plasma concentrations of aldosterone above individual basal concentrations was also reduced during the administration of human atrial natriuretic peptide, although this effect was only marginal during the low dose experiment. These effects of human atrial natriuretic peptide support the contention that its therapeutic impact in hypertensive patients might be mediated in part by a reduction of high aldosterone concentrations.

ISSN:0194-911X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

This report is based on three different representative population samples of a total of 1304 men (50–79 years old) and 1246 women (38–79 years old) observed for up to 12 years. Subject's consumption of antihypertensive drugs and blood pressure levels in subjects with and without such treatment are presented. The prevalence of treatment with antihypertensive drugs (including β-blockers and diuretics for other Indications) increased from 2% at age 50 years to 37% at 79 years of age among the men and from 1% at 38 years to 61 % at 79 years of age among the women. The mean systolic/diastolic blood pressure in untreated subjects increased from 138/91 mm Hg at age 50 years to 159/91 mm Hg at age 70 years in the men and from 123/79 mm Hg at age 38 years to 168/93 mm Hg at age 70 years in the women. At age 79 years the mean systolic/diastolic blood pressure was 155/83 mm Hg in the men and 161785 mm Hg in the women. In a longitudinal follow-up of reexamined subjects, there was an increase in systolic blood pressure levels up to age 75 years and a reduction in diastolic blood pressure after age 75 years in both sexes.

ISSN:0194-911X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

In a previous study, we demonstrated that the red blood cell Na+concentration and Na+, K+-ATPase activity are sex-dependent and race-dependent: a higher intracellular Na+concentration in blacks and men was associated with a lower Na+, K+-ATPase activity. To examine whether the low Na+, K+-ATPase activity is due to a decreased number of enzyme units, altered structure of the enzyme, or the presence of an endogenous digoxinlike substance, ouabain binding studies were performed on the same subject group. The measurements included displacement of [3H]Jouabain from its specific binding sites by unlabeled ouabain or potassium. The results demonstrate that groups with lower enzyme activity manifest lower numbers of total specific ouabain binding sites on the surface of the red blood cell (mean ± SD: blacks, 654 ± 24.4; whites, 806 ± 18.3; women, 806 ± 26.9; men, 728 ± 21.2). Other kinetic parameters of [3H]ouabain displacement appear to be the same among the groups. The respective red blood cell Na+and K+concentrations were negatively and positively correlated with the number of ouabain binding sites. Our findings suggest that the lower activity of red blood cell Na+, K+-ATPase in blacks and men is a function of a lower number of Na+-K+pump units. The results also indicate that sex and race should be considered when red blood cell ouabain binding is examined.

ISSN:0194-911X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Several operationally defined adenosine triphosphatase (ATPase) activities were determined in vitro in red blood cell lysates of normotensive or hypertensive humans: Mg2+-ATPase, Na+, K+-ATPase, and Ca2+ pump ATPase, the latter in the calmodulin-activated and basal states. Basal Ca2+pump ATPase was defined as the Ca1+-activated ATPase resistant tol(HM trifluoperazine. Subjects were part of a double-blind study in which treatment was divided into several phases: baseline (4 weeks), placebo or calcium (1 g elemental calcium/day, 8 weeks), placebo washout (4 weeks), placebo or calcium (1 g elemental calcium/day, 8 weeks). Irrespective of the phase of treatment, the basal Ca3+pump ATPase activity in red blood cell lysates of 36 hypertensive subjects was significantly less than that in lysates from 18 normotensive subjects. Other ATPase activities did not differ significantly, although all ATPases tended to be decreased in hypertension. The data are consistent with previous reports of altered membrane Ca3+binding and transport in hypertension, but the precise changes are not elucidated.

ISSN:0194-911X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

It has recently been reported that a low intake of calcium may be a risk factor for hypertension. In view of the contradictory results, even when the same survey data base has been used by different researchers, an in-depth analysis was undertaken of the data provided by the two cycles of the National Health and Nutrition Examination Survey (NHANES). Both surveys, conducted in consecutive 4-year intervals during the 1970s, were designed to examine representative samples of the U.S. civilian noninstitutionalized population. The overall descriptive findings in relation to mean blood pressure and calcium intake were virtually identical in the two surveys. Based on “quantile” analysis, neither mean levels of blood pressure nor the prevalence of hypertension was related to calcium intake. Only among black men in NHANES I was a relationship between calcium intake and blood pressure noted. This finding was not apparent among black men in NHANES II or among any of the other sex-race groups in either survey. We conclude that the data of NHANES I and H do not show an association between low calcium intake and blood pressure.

ISSN:0194-911X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The magnitude of the cardiovascular response to stress has been implicated in the pathogenesis of cardiovascular disease. Psychological stress procedures have received increased usage as an alternative to expensive physical (exercise) stress procedures. In the present investigation, 213 healthy, black or white, male or female children between the ages of 6 and 18 years were exposed to the psychological stress of a video game. The video game challenge was administered by a black or a white experimenter and was played under three levels of increasing stress, 1) personal challenge, 2) experimenter's challenge, and 3) experimenter's challenge accompanied by a financial incentive, while blood pressure and heart rate were monitored. Results indicated that the video games provoked significant and incremental cardiovascular reactivity across the games. Black children demonstrated significantly greater reactivity than white children; the racial difference was more reliably observed for systolic and diastolic blood pressure than for heart rate. Furthermore, the race of the experimenter exerted a significant effect and often interacted with the race of the child, such that greater reactivity occurred in same-race pairings than in mixed-race pairings. These results suggest that reactivity is affected by an individual's race and social milieu and that reactivity may be one mechanism responsible for the greater prevalence of hypertension among blacks.

ISSN:0194-911X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

A randomized, double-blind, placebo-controlled crossover trial of oral calcium supplementation was carried out in 18 patients with uncomplicated essential hypertension. After 15 weeks of oral calcium supplementation, 1 g/day, of the patient's habitual diet, the only blood pressure change (compared with the results of placebo treatment) was in the average standing systolic blood pressure, which was significantly reduced (−8.6 mm Hg;p< 0.01). The 24-hour urinary calcium excretion and the total serum calcium concentration increased significantly during calcium supplementation (p< 0.05), indicating good compliance with the treatment. The individual blood pressure changes with high calcium intake were found to be inversely related to basal 24-hour urinary calcium excretion (r = −0.69,p< 0.001 for standing systolic pressure; r = −0.55,p< 0.002 for standing diastolic pressure). This correlation was independent of age, basal blood pressure, serum calcium concentration, basal 24-hour urinary sodium excretion, and body weight changes during the trial. In particular, a subgroup of six patients, who had a basal 24-hour urinary calcium excretion higher than the mean + 2 SD of a reference healthy population previously described, showed a substantial average blood pressure fall at variance with the other patients in the study. These results do not support the usefulness of an oral calcium supplement in the majority of subjects with mild essential hypertension; however, they suggest that a group of patients with a previously reported abnormality of calcium metabolism may be responsive to this therapeutic measure.

ISSN:0194-911X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The purpose of these experiments was to study the possible contribution of bradykinin to normal blood pressure maintenance. The bradykinin analogue B4146, a competitive antagonistpartial agonist of bradykinin, was used in three groups of normotensive unanesthetized Wistar rats. Two intra-aortic injections of B4146 (1 mg in 0.2 ml of dextrose) were given 5 minutes apart (i.e., well after return of blood pressure to baseline, which occurred within 68 ± 19 seconds). One group had been pretreated with the angiotensin converting enzyme inhibitor HOE 498,1 mg/kg (Hoechst), and one received only dextrose as the first injection to serve as controls. The bradykinin antagonist produced an average increase in mean arterial pressure of approximately 13 mm Hg for all groups. In five animals, however, the first injection of B4146 produced a hypotensive effect, whereas the second one consistently produced a rise in blood pressure. Pretreatment with the angiotensin converting enzyme inhibitor did not affect the magnitude of the subsequent blood pressure increase in response to B4146.Since smaller doses of B4146, sufficient to block exogenous bradykinin, do not cause changes in normal blood pressure, we conclude that endogenous bradykinin does contribute to normal blood pressure maintenance, but its effect can be demonstrated only if very high doses of its antagonist are injected, maybe because a high concentration of the compound is necessary to displace not only circulating but possibly tissue receptor-bound bradykinin as well.

ISSN:0194-911X    

出版商:OVID    

年代:1986

数据来源: OVID