ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

An increased prevalence of hypertension in groups with high alcohol consumption has been recognized for a number of years. More recently, several studies have suggested an independent association between alcohol consumption and blood pressure levels in samples from general populations. Of 30 cross-sectional population studies reviewed, the majority reported small but significant elevations in blood pressure in those consuming three drinks or more per day in comparison with nondrinkers. In 25% of studies, elevations in blood pressure were also reported at lower levels of consumption; in about 40%, the blood pressure of nondrinkers was greater than that of those consuming one to two drinks per day. In two studies, one from the United States and one from Australia, the maximum contribution to the prevalence of hypertension of alcohol consumption greater than two drinks per day was estimated to be 5 to 7%; the contribution in men (11%) was greater than that in women because of their greater alcohol consumption. A prospective association of alcohol consumption with change in blood pressure was observed in five studies. In a small number of experimental studies, short-term falls in blood pressure accompanied alcohol restriction in both normotensive and hypertensive subjects. Uncontrolled observations in heavy drinking populations suggest that the effect on blood pressure of alcohol withdrawal may be lasting. However, firm conclusions about the long-term effects of alcohol restriction, particularly in moderate consumers who represent a large proportion in many populations, must await long-term controlled trials.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The local responses of the resistance vessels of the hindquarters of conscious, renal hypertensive (cellophane wrap) and sham-operated normotensive rabbits were studied during infusions of constrictor (norepinephrine, methoxamine, angiotensin II) and dilator (acetylcholine, adenosine, serotonin) drugs. The rabbits had implanted Doppler ultrasonic flow probes on the lower aorta and an indwelling catheter for intra-arterial infusion of drugs. Autonomic blockade with mecamylamine and propranolol was used to determine local vascular effects of each drug uncomplicated by reflex changes. Logistic dose-vascular response curves were characterized by (1) their range from resting to maximum response, (2) their 50% effective dose (i.e., sensitivity or dose at middle of the response range), and (3) the average slope about the 50% effective dose. At maximum dilatation the vascular resistance was about 70% greater in hypertensive rabbits than in normotensive rabbits. There were no significant differences in 50% effective dose values between curves for hypertensive and normotensive rabbits for constrictor or dilator drugs. However, with all drugs the hypertensive rabbits showed about twice the change in vascular resistance per unit dose compared with the normotensive rabbits. These results suggest that hypertrophy of the muscles of the precapillary vessels makes them a nonspecific amplifier of vascular resistance changes evoked by constrictor and dilator stimuli. They do not support previous claims of specific changes in “sensitivity” or claims that local amplifier action is unimportant in hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The central cardiovascular effects of the calcium channel blocker nifedipine and the calcium channel activator BAY k 8644 were studied in anesthetized and ventilated normotensive Wistar-Kyoto (WKY) or spontaneously hypertensive rats (SHR). Both drugs were administered in a 1.5-U.1 volume into the lateral ventricle of the brain (i.c.v.) or into the cisterna magna (i.e.). The injection of vehicle alone (i.e. or i.c.v.) did not significantly change mean arterial pressure (MAP) or heart rate. Nifedipine (5 and 50/ug/kg) and BAY k 8644 (5 and SO fig/kg) induced opposite effects on MAP when centrally injected. Nifedipine decreased MAP and induced a bradycardia (i.c.v.) or no change in heart rate (i.e.), and BAY k 8644 increased MAP without any significant change in heart rate (i.e. or i.c.v.). These effects were more marked with the highest dose of either drug. These effects seemed to be of central origin, since they were suppressed by gang!ionic blockade by hexamethonium (100 mg/kg i.v.), whereas after hexamethonium the hypotensive and the hypertensive responses to intravenously injected nifedipine and BAY k 8644, respectively, were preserved. Bilateral vagotomy suppressed the bradycardia induced by i.c.v. administered nifedipine. Previously i.c.v. administered nifedipine (5/u.g/kg) antagonized the pressor response to BAY k 8644 (5 jug/kg i.c.v.). Changes in MAP and heart rate were significantly more marked in SHR than in WKY. These results indicate that a calcium channel inhibitor and a calcium channel activator can modulate in opposite fashion central mechanisms involved in blood pressure control.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The influence of long-term alterations in dietary magnesium intake on blood pressure and on the antihypertensive effect of the calcium antagonist nifedipine was investigated in normotensive Wistar-Kyoto (WKY) and in spontaneously hypertensive rats (SHR). The rats were fed a diet either high (1%), normal (0.1%), or low (0.01%) in magnesium for 12 weeks (WKY) and 20 weeks (SHR), respectively. Nifedipine was added to the diet for 4 weeks in concentrations of 300 and 1000 ppm. Each dose was given for 2 weeks. Plasma and intraerythrocytic concentrations of sodium, potassium, and magnesium were measured before and at the end of nifedipine treatment. Blood was obtained by cardiac puncture. In the WKY and SHR, blood pressure was not influenced by magnesium intake. The blood pressure-lowering effect of nifedipine was most pronounced on normal dietary magnesium and was significantly suppressed in the magnesium-deficient rats. Plasma and intracellular total magnesium concentrations were consistently increased during high and reduced during low dietary intake of the ion. Intracellular sodium concentration increased during magnesium deficiency and was normalized by nifedipine. The marked and long-term alterations hi plasma and intracellular concentrations of magnesium did not influence arterial blood pressure levels in either the normotensive WKY or the SHR. Therefore, dietary magnesium intake does not appear to play an important role in long-term regulation of blood pressure in rats. However, magnesium depletion attenuates the blood pressure-lowering effect of nifedipine.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Atrial natriuretic factor (ANF) was studied in rat plasma and atria 1, 2, 4, 6, and 8 weeks after constriction of the left renal artery and removal of the contralateral kidney. Plasma ANF was elevated at all periods of investigation. A positive correlation was observed between plasma ANF and blood pressure (r = 0.56,p< 0.001). The total atrial ANF content (μg/atrium) in one-kidney, one clip (1K1C) rats was lower during Weeks 1 and 2, but only in the left atrium. Lower ANF concentrations (jig/mg protein) were also evident in the left atrium at Weeks 1, 2, and 8, and in the right atrium at Week 8. A negative correlation between ANF in plasma and in the left atrium was discerned (r = 0.43,p< 0.01). Blood pressure (184 ± 4 vs 114 ± 4 mm Hg), body weight, and plasma ANF were also examined in 1K1C rats and their normotensive controls before and after unclipping. Blood pressure was normalized 6 hours after unclipping. Plasma ANF declined in 1K1C rats within 6 hours after clip removal, but it was still higher than in the controls. Plasma ANF was similar in both groups on Days 9 and 13 after unclipping. There were no differences in atrial ANF between hypertensive and normotensive animals 13 days after unclipping. The high levels of plasma ANF observed in 1K1C rats probably are secondary to increased intra-atrial pressure caused by the dual mechanism of expanded plasma volume and high blood pressure.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The hypotensive efficacy of a potent new renin inhibitor (iVa-isovaleryl-L-histidyl-Lprolyl-L-phenylalanyl-L-hlstidyl-ACHPA-L-leucyl-L-phenylalanyl amide) containing (3S,4S)-4-amino-5-cyclohexyl-3-hydroxy pentanoic acid (ACHPA) was compared with the converting enzyme inhibitor (enalaprilat) (MK-422) in conscious one-kidney dogs before and after tightening a renal artery clamp. Dose-response curves to 0.003 to 0.1 mg/kg/min i.v. infusions of the ACHPA-containing renin inhibitory peptide or enalaprilat (0.003–0.1 mg/kg i.v. bolus) were obtained in one-kidney dogs before and 3 days and 14 days after renal artery constriction. The ACHPA-containing renin inhibitory peptide and enalaprilat maximally decreased blood pressure by 10 ± 2 and 9 ± 2 mm Hg before constriction and by 12 ± 2 and 12 ± 4 mm Hg in dogs treated 14 days after renal artery constriction, respectively. Glomerular filtration rate and effective renal plasma flow were unaltered or slightly improved. In sharp contrast, both compounds elicited significant, dose-related decreases in blood pressure (− 26 ± 4 and − 20 ± 4 mm Hg, respectively), glomerular filtration rate (− 21 ± 3 and −23 ± 3 ml/min), and renal plasma flow (−45 ± 14 and −48 ± 13 ml/min) in dogs examined 3 days after renal artery constriction. These data demonstrate that ACHPA-containing renin inhibitory peptide and enalaprilat are equally effective antihypertensive agents in dogs with renin-dependent renovascular hypertension and lend credence to the contention that the renin-angiotensin system supports renal function in hypertensive states in which renin levels are elevated.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Experiments were designed to study endothelium-dependent responses in salt-sensitive (DS) and salt-resistant Dahl rats (DR). The rats were fed a low sodium (0.1% NaCl) or high sodium (8% NaCl) diet for 8 weeks. Blood pressure in DS fed a high sodium diet was higher than that in the remaining animals. Aortic rings with and without endothelium were suspended for isometric tension recording. Acetylcholine, adenosine 5′-diphosphate, and thrombin induced endothelium-dependent relaxations that were significantly depressed in the aorta of DS fed a high sodium diet. The relaxations in response to sodium nitroprusside were only slightly, but significantly, depressed in DS fed a high sodium diet. Removal of the endothelium greatly enhanced the response to serotonin and norepinephrine. In rings with, but not without, endothelium taken from rats fed a high sodium diet, the tension developed in response to serotonin and norepinephrine was significantly greater than that in animals fed a low sodium diet. These experiments indicate that (1) endothelium-dependent relaxations to acetylcholine, adenosine 5′-diphosphate, and thrombin are depressed in hypertensive Dahl rats; (2) this effect probably reflects a decreased release of endothelium-derived relaxing factor(s), although structural changes might contribute; and (3) the responsiveness to vasoconstrictor agents is increased in DS and DR fed a high sodium diet. These findings may indicate differential effects of blood pressure and dietary salt on endothelial function.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We studied the degree of arteriolar smooth muscle constriction in the spinotrapezius muscle microcirculation of spontaneously hypertensive rats and their normotensive controls, Wistar-Kyoto rats. The constriction was expressed in the form of a nondimensional tone as the difference between steady state and dilated diameter (after papaverine treatment) divided by the dilated diameter. Both animal strains showed on average a progressive increase of tone toward the more distal arterioles, with a peak tone being reached in the transverse arterioles. Tone values in the hypertensive animals were consistently elevated. The number of arterioles that had more than 5% tone (so-called responder arterioles) was higher in the hypertensive animals. These studies suggest that, besides the anatomical adjustments documented earlier in our laboratory in the arteriolar network of this muscle, functional adjustments in the form of an elevated microvascular tone are associated with the elevated resistance in spontaneously hypertensive rats.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

To investigate a possible sex difference in the development of deoxycorticosterone (DOC)-salt hypertension in rats, systolic blood pressure was measured over 6 weeks in unilaterally nephrectomized male and female rats with or without DOC-salt treatment. Throughout the treatment, systolic blood pressure was significantly lower in female than in male DOC-salt rats (at the end of the sixth week: 190 ± 8 vs 163 ± 7 nun Hg,p< 0.05). The difference in blood pressure was also confirmed by the direct measurement of mean arterial pressure at the end of the experiment. The 24-hour urinary excretion of vasopressin was significantly higher in male control rats than in female control rats; however, no difference was observed between male and female DOC-salt rats, in which the urinary excretion of vasopressin was four to five times higher than in control rats. The plasma vasopressin concentration was higher in DOC-salt rats, but there were no differences between sexes. These were no differences in the metabolic clearance rate of vasopressin among the four groups of rats. This indicates that the elevated plasma vasopressin concentration in DOC-salt hypertensive rats is due to increased release of the hormone, rather than to impaired metabolism. Thus, although vasopressin plays a pivotal role in the pathogenesis of DOC-salt hypertension, the sexual dimorphism in this form of hypertension cannot be attributed to differences in the secretion, metabolism, or plasma concentration of vasopressin.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID