ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

This study was designed to investigate the effects of dietary modification of prostaglandin (PG) synthesis on blood pressure regulation in spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats under conditions of normal and elevated salt intake. Forty rats from both strains were placed on either a two-series PG inhibitory diet of Max eicosapentaenoic acid (EPA) fish oil or a control diet of saturated fat for an initial period of 4 weeks. The groups were then divided into two, so that half of each received 1.5% saline in place of their drinking water for 1 week. Blood pressure of the SHR and WKY were unaffected by dietary fat before the addition of saline, but with salt loading, the Max EPA-fed SHRs showed a mean blood pressure increase of 21 mmHg relative to the EPA-fed SHR with access to water. Rats fed EPA showed impaired ability to generate serum thromboxane (TXB2) and in the groups with access to water, diminished excretion of urinary 6-keto-PGF1αand PGE2. Salt loading increased prostanoid synthesis and excretion. Spontaneously hypertensive rats had greater serum TXB2generating capacity than WKYs, but diminished urinary PGE2excretion in those animals with access to water. The increased blood pressure observed in the salt-loaded SHR on the Max EPA-diet may be explained by reduced PG synthesis resulting in either mild sodium retention and/or increased vascular reactivity.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

In order to evaluate the use of Doppler echocardiography in the assessment of the haemodynamic effects of antihypertensive drugs, the acute haemodynamic response to felodipine and additional administration of metoprolol after 90 min was assessed in 10 hypertensive patients, by using both the Fick method and Doppler blood flow velocimetry in the ascending aorta. Intrabrachial artery pressure was significantly reduced by the treatment. Both the Fick and Doppler estimates of cardiac output (CO) rose significantly with felodipine and reached their highest values after 30 min, 45 ± 8% (s.e.m.) and 58 ± 7%, respectively. The felodipine-induced increase of heart rate (HR) persisted for 90 min, but the increase of stroke volume was only transient. Metoprolol brought CO and HR back to control levels. The felodipine- and metoprololinduced changes of CO and stroke volume (SV) from control were on average not different between the observations with the Fick and the Doppler techniques throughout the study. As for the absolute values (control period), the Doppler measurement underestimated SV (10 ml) and CO (1.1 l/min) in comparison with the Fick method, and the limits of agreement (mean difference ± 2 s.d.) between both methods were 42 and —22 ml for stroke volume and 3.4 and —1.2 l/min for CO. In conclusion, despite the poor agreement in absolute results between the two methods, aortic Doppler velocimetry reflects the acute haemodynamic changes induced by felodipine and metoprolol in a group of hypertensive patients. The technique should facilitate the study of haemodynamic effects of drugs in man.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Angiotensin converting enzyme (ACE) activity in human plasma and cerebrospinal fluid (CSF), was measured by a fluorimetric method, following an acute oral dose (75 mg) of captopril. A decrease of approximately 60% in enzyme activity was observed in CSF, suggesting that the drug penetrates the blood/brain barrier (BBB) in sufficient amounts to inhibit the ACE in CSF. The activity of CSF enkephalinase, an enzyme present in human brain and inhibited invitroby an elevated concentration of captopril, was, however, unaffected by the acute drug administration. It is proposed that the antihypertensive effect of captopril in humans may be due, at least in part, to the inhibition of ACE contained within brain structures.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The possible role of the vascular angiotensin converting enzyme (ACE) in the development of two-kidney, one clip (2-K.1C) hypertensive dogs was studied in different blood vessels. Vascular ACE activity per mg protein differed in a variety of blood vessels; the activity appeared to vary inversely with the outer diameter of arteries. The systemic blood pressure in mongrel dogs increased after partial occlusion of the left renal artery, and the hypertension lasted for 8 months. Plasma renin activity (PRA) was raised only for the first 4 weeks after the operation and then returned to the original level in the chronic stage of hypertension. Plasma ACE activity did not alter during the experimental period. In contrast, ACE activities in the jejunal, pulmonary and renal arteries, aorta, lung and cerebral cortex, significantly increased in the chronic hypertensive stage (8 months after occlusion). The production of angiotensin II (ANG II) from ANG I was significantly greater in isolated arteries from 8-month hypertensive dogs than in those from normotensive dogs when assessed by the contractile responses to ANG I and ANG II. These results indicate that acceleration by increased vascular ACE activity of the production of ANG II in the vascular wall may contribute to the maintenance of hypertension in the chronic stage of 2-K,1C hypertensive dogs having normal PRA and plasma ACE activity.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

This study characterizes contractions to ouabain and potassium-free solution in isolated vascular segments from two-kidney, one clip (2-K, 1C) hypertensive rats. Aorta, mesenteric artery, and vena cava from hypertensive rats were more sensitive (lower threshold) to ouabain than those from normotensive rats. Contractions of hypertensive vascular segments to potassium-free solution and to ouabain (10-3mol/l) were faster than those in normotensive vessels. Monensin potentiated contractions to ouabain and increased the rate of force development to potassium-free solution to a greater extent in normotensive aortae than in hypertensive aortae. Amiloride, low sodium solution, verapamil and calcium-free solution depressed contractions to ouabain and potassium-free solution in both hypertensive and normotensive aortae. These observations demonstrate augmented responsiveness to ouabain and potassium-free solution in hypertensive blood vessels. Interventions which influence transmembrane sodium and calcium movements altered contractions to ouabain and potassium-free solution. The results are consistent with the hypothesis that vascular cells of hypertensive rats have enhanced sodium pump activity.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The arterial hypertension that frequently coexists with ventromedial hypothalamic (VMH) lesion-induced obesity has been obtained in rats chronically sustained on diets of standard-to-high salt content. Since VMH lesions also compromise the renal circulation and enhance ingestion of salt-loaded diets, the resulting haemodynamic adjustments, including hypertension, have been interpreted as possibly being sodium-dependent. This notion implies that chronically restricting dietary salt would ameliorate the hypertension, whereas the persistence of hypertension under such a regimen would suggest the potential contribution of non-sodium-related factors. This study assessed whether chronic maintenance of a low-salt diet would buffer the hypertensive and haemodynamic consequences of obesity, accompanying electrolytic VMH lesions in male Wistar-Kyoto (WKY) rats, compared with sham-treated controls. Despite the low-salt diet, the results showed that VMH obesity was accompanied by hypertension, elevated plasma norepinephrine, and redistribution of blood flow away from the brain, kidney and splanchnic organs. The compatibility of these results with earlier studies permitting salt ingestion, is difficult to reconcile with the notion that VMH-hypertension is sodiumdependent. Instead, it suggests that the VMH obesity-hypertension syndrome may provide a useful model for clarifying the autonomic consequences of either augmented carbohydrate ingestion of hyper-insulinaemia.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Quantitative evaluation of brachial artery diameter, blood velocity and flow (pulsed Doppler velocimetry) and of forearm arterial compliance (FAC) - mathematical analysis of the simultaneous diastolic pressure and flow according to a first-order arterial model - was carried out in 10 normotensive controls, and in 23 borderline hypertensive patients, of the same age. Using a value of 2 standard deviations above the average cardiac index of 20 normotensive subjects, enabled us to classify 12 patients as having a normal cardiac output and 11 patients as having a high cardiac output. Each group was of similar age and pressure. FAC was lower in patients with a normal cardiac output than in normal controls (P<0.01) and also lower than in patients with high output (P<0.01). Brachial artery diameter and flow were higher in patients with high output than in normal controls (P<0.01,P<0.001) and also higher than in patients with a normal output (P<0.001). A positive correlation (r=0.55;P<0.01) was found between heart rate and brachial artery diameter in the 23 patients. These results demonstrate a non-homogenous pattern of brachial artery characteristics of patients with borderline hypertension. Patients with normal cardiac output exhibited a clear reduction of the distensibility of the forearm arteries while patients with high cardiac output had strong dilation, of the brachial artery.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The haemorheological disturbances observed in primary hypertension arise mainly from haemoconcentration, which leads to an elevation of blood and plasma viscosity and increased aggregation of red blood cells (RBCs). We evaluated the rheological properties of blood and central haemodynamic indices in 13 men with untreated primary hypertension (WHO stage I and II), during a baseline period and after intravenous infusion of 1000 ml of 0.9% NaCI (within 12-15 min). The rheological properties studied were: whole blood viscosity (WBV), plasma viscosity (PV), haematocrit (HCT) and plasma fibrinogen concentration (PF). The central haemodynamic indices were: mean intra-arterial blood pressure (MAP), central venous pressure (CVP), cardiac index (Cl), stroke volume index (SVI), total peripheral resistance index (TPRI) and the vascular hindrance index (VHI). Plasma renin activity (PRA) and plasma noradrenaline concentration (P-NA) were also measured.Volume expansion with saline caused haemodilution as expressed by a fall in HCT (P<0.001), WBV (P< 0.001) and PV (P<0.01). At the same time, CVP, MAP and VHI increased (P<0.05) while PRA decreased (P<0.05) and P-NA remained unchanged. Mean values of the cardiac index (Cl) and stroke volume index (SVI) did not change significantly. We did not observe any significant relationship between haemodynamic and haemorheological parameters, during baseline or between their respective changes after the infusion.The results indicate that although hypervolaemic haemodilution produced by saline infusion in hypertensive patients may improve blood flow properties (HCT, WBV, PV), blood pressure (BP) is not reduced; rather the converse is true. The reduction in HCT and hence the improved blood rheology, did not affect calculated vascular resistance. Thus, correction of WBV does not acutely normalize BP in primary hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1987

数据来源: OVID