ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

65% relaxation of a maximal endothelin-induced contraction in the presence of normal extracellular sodium. However, in the presence of a low extracellular sodium concentration, inhibition of Na-H exchange only resulted in a 25% relaxation. These data suggest that endothelin-induced vasoconstriction of human peripheral resistance vessels is mediated in part by stimulation of Na-H exchange.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The activity of ion-transport systems and Ca2+-induced erythrocyte haemolysis were compared between patients with essential hypertension and two strains of spontaneously hypertensive rats. Previous data on the increased rate of Na+-Li+countertransport in erythrocytes of essential hypertensives were confirmed in this study. However, identification of Na+-Li+countertransport in rat erythrocytes remained a complicated problem because of the high rate of sodium-independent efflux of Li+. The rate of Na+-H+exchange increased by 50-80% both in spontaneously hypertensive Wistar-Kyoto rats (SHR) and in patients with essential hypertension. No difference between Milan hypertensive strain rats (MHS) and Milan normotensive strain rats (MNS) was found.The rate of Na+,K+cotransport increased in SHR and MHS erythrocytes compared with rats of the control strains [normotensive Wistar-Kyoto rats (WKY) and MNS; 30-50 and 90-110%, respectively]. No difference in this parameter was found between patients with essential hypertension and healthy subjects. Erythrocytes of patients with essential hypertension and of SHR were characterized by a higher sensitivity of their K+channels to the increased concentration of intracellular Ca2+. This parameter did not change in MHS erythrocytes. Ca2+-induced haemolysis increased four- to fivefold in MHS erythrocytes compared with MNS and did not change in erythrocytes of SHR and patients with essential hypertension.The conclusion from these data is that the SHR strain is a more adequate model of human essential hypertension than the MHS.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Local vascular generation of angiotensin was investigated in isolated perfused rat hindquarters. Extraction and combined high-performance liquid chromatography (HPLC)/ radioimmunoassay analysis of hindlimb perfusate showed a spontaneous release of angiotensin I (Ang l; 5.0 ± 3.4fmol/h) and angiotensin II (Ang ll; 31.8 ± 7.9 fmol/h). Angiotensin converting enzyme (ACE) inhibition with captopril abolished Ang II release while Ang I levels increased more than 10-fold. Perfusion with purified hog renin caused a dose-dependent angiotensin release and vasoconstriction. The renin inhibitor H-142 abolished all effects of renin whereas ACE inhibition prevented Ang II formation and vasoconstriction but increased Ang I levels. Metabolism and pressor effects of synthetic tetradecapeptide renin substrate (TDP), Ang I and Ang II were studied using a recirculating rat hindlimb perfusion system. TDP-dependent formation of Ang I and II, and an increase in perfusion pressure was shown; ACE inhibition reduced but did not abolish Ang II formation and vasoconstriction. Ang I was converted to Ang II by about 50% during one pass through a hindlimb. This conversion was abolished by ACE inhibition. These data add support to the presence of a functional vascular renin-angiotensin system.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The relative influences of sympathetic and parasympathetic neural modulation on mean arterial pressure (MAP) and heart rate (HR), and their respective variabilities, were studied in young spontaneously hypertensive rats (SHR) and Wistar–Kyoto rats (WKY). An on-line computerized system was used for continuous intra-arterial measurements of MAP and HR in unrestrained rats. In addition, the autonomic nervous control of MAP and HR was studied in ageing SHR and WKY. Both WKY and SHR showed diurnal rhythms with regard to MAP and HR. The MAP variability was higher in SHR than in WKY during both daytime (inactive) and night-time (active), and did not change in response to either β1-adrenoceptor- or cholinergic blockade. Structural vascular changes, with a resultant increase in reactivity, may explain the elevated MAP variability in SHR. HR variability was clearly reduced in SHR; this was not influenced by vagal blockade, whereas HR variability was significantly reduced in WKY. This pattern is suggested to be due to a reduced tonic vagal discharge in SHR, as part of a persistent, mild defence reaction. The initial reduction in vagal activity will in turn eliminate vagally mediated tachycardias. Furthermore, administration of β1-blockade to SHR of different ages caused a greater fall in MAP and HR than in WKY, indicating an increased dependence upon the sympathetic nervous system in SHR with age.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Probes to hypervariable minisatellite regions of DNA identify multiple loci scattered over the autosomal chromosomes and produce a complex Southern blot pattern of fragments termed a DNA 'fingerprint'. As concern has been raised that different stocks of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) may not be biologically identical, we have compared the DNA of SHR and WKY from several sources using two such probes which identify different sets of minisatellite sequences. While the DNA fingerprints of SHR from the various sources were identical, variability was observed in those of WKY, indicating genetic heterogeneity between different WKY stocks. In animals from one of the commercial suppliers even inter-rat variability in DNA fingerprints was seen, suggesting genetic heterogeneity within that single colony. These observations indicate that experimental results obtained using WKY from different sources may not be directly comparable and could provide an explanation for some of the conflicting data that exist on the comparative characteristics of SHR and WKY. In separate studies, direct comparisons both of the DNA fingerprints of SHR and WKY and of SHR and stroke-prone spontaneously hypertensive rats (SHRSP) showed multiple differences between the strains. The polymorphisms seen could provide useful linkage markers in locating the chromosomal sites of the genetic loci responsible for raised blood pressure in the SHR and the propensity to strokes in the SHRSP.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

This study compared the antihypertensive effects and the haemodynamic mechanisms of action of an angiotensin converting enzyme (ACE) inhibitor, a β-blocker and the combination of both in patients with mild to severe hypertension. After a placebo run-in period of 2 weeks, patients were treated for 3 weeks with each of the following: cilazapril (2.5 mg daily) and propranolol (120 mg daily), in a randomized sequence, and thereafter a combination of the two drugs. Blood pressure, cardiac output (measured by Doppler ultrasound) and total peripheral resistance (TPR) in a sitting position at rest were determined. One patient out of 18 was withdrawn in the cilazapril phase. Both monotherapies yielded significant and similar reductions of diastolic blood pressure (average -10mmHg). Cardiac output and TPR showed opposite effects. Cardiac output was lower with the β-blocker than with the ACE inhibitor (3.4 versus 4.5l.min−1), while TPR behaved conversely (2646 versus 2005 dyne. s. cm−5). The combination of both drugs lowered diastolic blood pressure significantly more than the monotherapies (average — 20mmHg); the haemodynamic effects of the monotherapies were attenuated by the combination (cardiac output=3.7l.min−1; TPR=2170dyne.s.cm−5). A sitting diastolic blood pressure of ≤90mmHg could be achieved in six out of 17 patients with propranolol alone, in eight out of 18 with cilazapril alone, and in 14 out of 17 with the coadministration of both drugs. The combination was better tolerated subjectively than the β-blocker alone.It was concluded that the combination of an ACE inhibitor and a β-blocker can be an effective and well tolerated antihypertensive regimen and should no longer be excluded from therapeutic consideration.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

In order to investigate whether angiotensin II (Ang ll) may contribute to cardiovascular regulation through facilitation of the adrenergic function, we examined the haemodynamic and humoral effects of the application of lower-body negative pressure (LBNP) in sodiumreplete patients with essential hypertension before and after acute and chronic angiotensin converting enzyme (ACE) inhibition. We measured the changes in blood pressure, heart rate, central venous pressure, forearm blood flow, plasma noradrenaline, renin activity and Ang II induced by LBNP of two different magnitudes: a milder one deactivating predominantly the cardiopulmonary receptors (mild LBNP), and a greater one deactivating both the cardiopulmonary and the arterial baroreceptors (strong LBNP). We found that during mild LBNP systemic blood pressure was maintained after acute and chronic ACE inhibition, as in control studies; however, the decrements in forearm blood flow and the increments in forearm vascular resistance caused by LBNP were diminished after ACE inhibition (the latter by 69 and 67%, respectively, in acute and chronic studies), in spite of the fact that the falls in central venous pressure and the increases in noradrenaline (NA) were similar to those observed in control conditions. During strong LBNP, the fall in systemic blood pressure was greater after acute and chronic ACE inhibition than in control conditions and was associated with a reduction in the response of forearm vascular resistance similar to that observed during mild LBNP, while the increments in NA were again superimposable to those seen before ACE inhibition. These alterations in the haemodynamic responses to LBNP induced by ACE inhibition were associated with significant increments in basal plasma renin activity and with marked reductions in Ang ll. These findings suggest that even in the sodium-replete state, Ang II exerts a facilitatory action on adrenergic function that is physiologically relevant for the regulation of forearm blood flow and the maintenance of blood pressure during the application of gravitational stresses.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The development of hypertension care in Finland was evaluated using the data from two independent population samples of the FINMONICA Project comprising 9350 and 6250 persons examined in 1982 and 1987, respectively. The sampling frame was the population aged 25 to 64 years in the provinces of North Karelia and Kuopio in eastern Finland and in the Turku-Loimaa region in south-western Finland. During the 5-year period, the mean systolic blood pressure levels decreased in all of the groups except the North Karelian men. Mean diastolic blood pressure did not change significantly. The proportion of hypertensive men with adequately controlled blood pressure increased from 22.6 to 29.4% [difference 6.8%, 95% confidence interval (Cl) for the difference 2.4-11.2] during 1982-1987. At the same time, the proportion of hypertensive men unaware of their condition fell from 30 to 20.9% (difference −9.1%, 95% Cl for the difference −13.4-−4.8). There were corresponding falls for women from 39.2 to 41.3% (difference 2.1%, 95% Cl for the difference −3.1−7.3) and from 15.4 to 13.1% (difference -2.3%, 95% Cl for the difference 1.4-−6.0), respectively. Thus, obvious progress had taken place, although the situation remained far from satisfactory. The possibility of overly aggressive treatment of hypertension was also investigated. It was found that only <10% of the middle-aged hypertensive men treated with drugs had diastolic pressures ≤85mmHg, suggesting that this might not be an issue of concern at community level.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID