ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

In order to investigate whether resistance arterioles from spontaneously hypertensive rats (SHR) were more alkaline than those from Wistar-Kyoto rats (WKY), mesenteric arterioles were mounted in a myograph and loaded with the pH-sensitive dye 2,7-bis (carboxyethyl)5,6-carboxyfluorescein (BCECF). At 5 weeks of age the arterioles from SHR were significantly more alkaline compared with WKY vessels, at a time when the blood pressure was rising and media: lumen ratio was increasing in the hypertension-prone animals. At 12 weeks this difference was not present due to a non-significant rise in intracellular pH in WKY arterioles. Activation of the vessels with high K+depolarizing solution or noradrenaline induced an acid change in pH but no subsequent alkalinization was apparent. These results suggest that resistance arterioles from SHR are more alkaline than WKY vessels when the blood pressure is rising and their structural architecture is being modified, and the alkaline cytoplasmic pH may be contributing to the generation of the structural excess seen in these vessels in established hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Little is known about the relationship between blood pressure and endogenous sex steroid hormones in patients with essential hypertension. Studies in hypertensive men have described decreased androgens. Men with cardiovascular disease may have estrogen levels which are increased or similar to healthy controls. We measured selected sex steroid hormones in 24 medication-free patients with uncomplicated essential hypertension (diastolic blood pressure ≤90mmHg) and 24 normotensive subjects. The groups were equally divided by race, gender, age and weight. Hypertensive men had lower levels of both free and total testosterone and androstenedione than controls. The converse was true for hypertensive women. Androgen levels were similar in blacks and whites regardless of gender or blood pressure. Estradiol levels were higher in hypertensive men and women than controls and in blacks than whites. Levels of luteinizing hormone and sex hormone binding globulin were similar in all subjects. The clinical and pathophysiological significance of our findings merits further investigation.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The role of central nervous system α2-adrenoceptors in the regulation of peripheral sympathetic outflow to regional vascular resistance beds during environmental stress was examined in conscious chronically instrumented spontaneously hypertensive rats (SHR). SHR were instrumented with pulsed Doppler flow probes on the renal and mesenteric arteries and the lower abdominal aorta. The mean arterial pressure (MAP), heart rate and regional vascular resistance responses to air jet stress were determined before and after cumulative administration of the α2-adrenoceptor agonist, guanabenz, into the lateral cerebral ventricle in doses of 5 and 25μg. Compared with intracerebroventricular (i.c.v.) administration of isotonic saline vehicle which did not affect baseline systemic and regional haemodynamic measurements, guanabenz produced significant decreases in baseline MAP and heart rate but did not affect regional vascular resistances. During air jet stress, the characteristic pattern of the classic defense reaction with an increase in MAP, heart rate, renal and mesenteric vascular resistances and a decrease in hindquarters vascular resistance was observed and was not affected by i.c.v. administration of isotonic saline vehicle. Guanabenz did not affect the MAP, heart rate or renal vascular resistance responses to air jet stress. The air jet stress-induced increase in mesenteric vascular resistance was reduced by 25 μg guanabenz. The air jet stress-induced decrease in hindquarters vascular resistance was converted to an increase by 25 μg guanabenz. These results demonstrate that the regulation of environmental stress-stimulated sympathetic neural outflow to different vascular beds may be independently controlled by central nervous system α2-adrenoceptors.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The expression of two oncogenes (cone) c-myc and c-fos, coding for nuclear proteins which play a regulatory role in growth and differentiation, and of two genes coding for two heat shock proteins (HSP) 68 (molecular weight 68000) and 70 (molecular weight 70000), which have a protective function during stress, have been investigated by Northern blot analysis of the total RNA, extracted from adult rat ventricle and aorta. (1) The two one transcripts are absent from these tissues but their expression can be enhanced by a pretreatment with cycloheximide. (2) The HSP70 is, in part, constitutive, while HSP68 is not; both are thermo-inducible in an isolated coronary perfused rat heart. (3) The four messenger RNA (mRNA) are expressed in both ventricles and aorta, 1 or 2 hours after i.p. injection of 6mg/kg phenylephrine or 12 lU/kg of vasopressin. (4) They are also induced by a continuous or discontinuous injection of angiotensin II (7.5μg/kg per min) for 1–2 h, but only in the aorta. The lack of ventricular response to angiotensin II in rat ventricles has been attributed to the lack of angiotensin II receptors in this tissue. This indicates that, in addition to mechanical factors, circulating hormones which have in common the use of the phosphoinositol pathway, may activate the expression of genes coding for regulatory proteins. This may play a role in the genesis of both ventricular and aortic hypertrophy.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

It is now well established that structural changes in resistance vessels contribute to the long-term maintenance of many forms of hypertension. This study measured the time course of structural change in smaller resistance vessels during the development of de-oxycorticosterone acetates (DOCA) hypertension and after cessation of DOCA in Wistar rats by histometric assessment of cross-sections of renal arterioles. The relationship of structural change to blood pressure was assessed by preventing hypertension during DOCA treatment with hydralazine. Blood pressure rose progressively during DOCA treatment reaching 192 ± 3mmHg compared with 132 ± 2mmHg in controls after 10 weeks. Five and 10 weeks after cessation of DOCA, following 10 weeks of DOCA treatment, post-DOCA reversal of hypertension was only partial. Medial area to internal elastic lamina (IEL) radius ratio, wall to lumen ratio and intimal area to IEL radius ratio of renal arterioles increased progressively during 10 weeks of DOCA treatment with partial reversal of the increased medial area and wall to lumen ratio 5 weeks post-DOCA. Hydralazine completely prevented hypertension in DOCA rats and also largely prevented structural change.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Platelet free cytosolic calcium (PFCC) was measured in 21 healthy volunteers before and after cigarette smoking or physical exercise. The aim was to investigate whether acute blood pressure changes and increases in circulating levels of catecholamines and vasopressin modify PFCC. PFCC was determined using the Quin-2 method. Following cigarette smoking, significant increases in blood pressure, heart rate, plasma epinephrine (35 ± 18pg/ml before versus 51 ± 31 pg/ml after smoking,P< 0.05, mean ± s.d.) and vasopressin levels (0.8 ± 0.3 pg/ml before and 4.2 ± 4.1 pg/ml after smoking,P< 0.001) were observed. However, despite these acute hormonal and hemodynamic changes, PFCC remained stable at 156 ± 55nmol/l prior to the study and 157 ± 29nmol/l and 156 ± 38nmol/l at 20 and 80min post-smoking, respectively. Acute physical exercise led to an increase in heart rate and systolic blood pressure but to a decrease in diastolic pressure. Moreover, a marked increase in plasma norepinephrine levels was observed after exercise (213 ± 71 pg/ml before versus 747 ± 501 pg/ml after exercise,P± 0.001). Again, PFCC was stable at 185 ± 56nmol/l at baseline versus 188 ± 51 nmol/l at 20min and 155 ± 26 nmol/l at 80min after exercise. These results therefore demonstrate that PFCC is not influenced acutely either by blood pressure increases, or by elevations in circulating catecholamine and vasopressin concentrations.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Factors which determine sodium chloride sensitivity, defined as the difference between the mean blood pressure after 1 week of a low sodium chloride diet (3g/day) and that after 1 week of a high sodium chloride diet (20g/day), were studied in 60 inpatients with essential hypertension using a multivariate analysis. The sodium chloride sensitivity was independently correlated with the change in erythrocyte sodium concentration (r= 0.47) and with the change in plasma renin activity (r= 0.29), but it was not related to basal blood pressure, the change in plasma volume or the change in plasma norepinephrine concentration. These data suggest that both intracellular sodium accumulation and inadequate suppression of the renin-angiotensin system may be independently involved in the elevation of blood pressure after sodium chloride loading. We could not find the independent importance of volume retention, hyperadrenergic activity or basal blood pressure in the sodium chloride sensitivity.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The acute effect on the lower limit of cerebral blood flow (CBF) autoregulation of an angiotensin converting enzyme (ACE) inhibitor, captopril, was studied in normotensive volunteers and in hypertensive patients. Baseline CBF was measured using xenon-133 inhalation tomography, and changes in CBF were measured using the arterio-venous oxygen difference method. Cerebral blood flow autoregulation was studied in two separate normotensive groups, one group of 12 volunteers serving as a control, and one group of 12 volunteers studied after the administration of captopril 50 mg. In a group of seven hypertensive patients CBF autoregulation was studied before and 1 h after the administration of captopril 25 mg. In the normotensive volunteers the median lower limit of CBF autoregulation was 83 and 74mmHg in the untreated and the captopril-treated group, respectively, with no significant difference between the two groups. In five of the hypertensive patients the lower limit of CBF autoregulation was lowered by captopril, in median by 22mmHg. However, in two patients it was increased, by 3 and 13mmHg, respectively. It is proposed that the shift in the lower limit of CBF autoregulation seen in some of our cases, and which has previously been documented in experimental studies, may be dependent on the activity of the sympathetic nervous system.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The effect of haemorrhagic hypotension on plasma catecholamine levels was studied in anesthetized normotensive and DOCA–salt hypertensive rats. The basal levels of plasma norepinephrine (NE) were significantly higher in DOCA–salt hypertensive rats than in normotensive rats. Moreover, the elevations in plasma NE and epinephrine (E) levels induced by haemorrhagic hypotension were found to be markedly potentiated in DOCA–salt hypertensive rats. Pretreatment with the re-uptake blocker (desmethylimipramine) increased both basal and haemorrhage NE levels in DOCA–salt hypertensive as well as in normotensive rats. Consequently, basal and haemorrhage NE plasma levels remained significantly higher in the DOCA–salt hypertensive animals than in the normotensive rats even following neuronal re-uptake blockage. This suggests that the elevated NE concentrations found in the plasma of DOCA–salt hypertensive rats both under basal condition and during haemorrhagic hypotension do not reflect a defective re-uptake. Moreover, in contrast with what is observed in normotensive animals, bilateral adrenalectomy did not induce any increase in basal or haemorrhage NE levels in the DOCA-salt hypertensive rats. This constitutes yet more evidence supporting the existence of an impaired balance of the sympathoadrenal axis in this hypertension model. The present study therefore suggests that the potentiated plasma catecholamine response to haemorrhage in DOCA-salt hypertensive rats is the consequence of an increased sympathoadrenal reactivity and not of an altered neuronal uptake. This hyperreactivity may result from an impaired regulation of the sympatho-adrenal axis in that hypertension model.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID