摘要:

Several lines of evidence indicate that the parathyroid gland plays a role in blood pressure regulation. To examine whether the attenuation of the development of hypertension by parathyroidectomy is associated with modifications in cellular calcium metabolism, intracellular free calcium was determined in fura-2-loaded platelets of spontaneously hypertensive rats after parathyroidectomy. Parathyroidectomy decreased systolic blood pressure (146 ± 8 versus control 160±5mmHg, n=8 and 9, respectively; P<0.05) and serum ionized calcium (0.81 ± 0.08 versus 1.28 ± 0.04 mmol/l; P<0.01). However, no effect of parathyroidectomy on basal intracellular free calcium was detected (63.1 ± 5.5 versus 65.0 ± 5.1 nmol/l). Furthermore, there were no differences in the intracellular free calcium responses to thrombin in the presence and absence of external calcium, intracellular calcium discharge capacity or calcium extrusion from the cytosol. These results indicate that parathyroidectomy lowers blood pressure independently of alterations in platelet calcium handling

ISSN:0263-6352    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Thirty-six, 19-year-old men within the 95th percentile of mean blood pressure (110mmHg) at a routine medical screening were randomized into two groups and requested to return for a follow-up visit in 2 weeks. One group was sent a neutral letter, while the other was sent a letter conveying the information that their blood pressures were elevated. After 15min sitting in the laboratory, there was a significantly higher heart rate (P<0.05) in the informed group. Thirteen informed and 13 uninformed subjects were examined further by intra-arterial blood pressure recording and serial sampling of arterial catecholamines during cold pressor and mental stress tests. The study was undertaken examiner-blind. Informing the subjects of high blood pressure increased both baseline plasma noradrenaline (P<0.01) and adrenaline (P<0.05) and intraplatelet noradrenaline (P<0.05). Blood pressure (P<0.05) and heart rate (P<0.05) increased significantly more in the informed group when the subjects were told of the cold pressor test. In addition, there were exaggerated adrenaline (P<0.05) and diastolic blood pressure (P<0.05) responses to mental stress in the informed group. Thus, awareness of high blood pressure in young men may increase sympathetic tone and responses as measured in the laboratory. Conclusions from studies on early pathogenesis of essential hypertension should therefore be drawn with more caution when patients are aware of their high blood pressure

ISSN:0263-6352    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Several investigators have demonstrated the antihypertensive properties of potassium in various models of hypertension. The present studies were conducted to determine whether central mechanisms contribute to these salutary effects of potassium. In Inactin-anaesthetized rats, intracerebroventricular administration of KG solutions (0.375, 0.75 and 1.25 μmol/5μI) produced concentration-dependent reductions in arterial pressure and heart rate. These effects were significantly attenuated by prior central administration of ouabain, a selective inhibitor of the sodium pump. In a separate series of experiments, prior central administration of α1and α22-antagonist phentolamine, or the dopamine receptor (DA1and DA2) antagonist RS-sulpiride, was also effective in inhibiting the hypotensive and bradycardiac effects of intracerebroventricular administration of potassium. Thus, these data suggest that activation of Na+, K+-ATPase and central noradrenergic and dopaminergic mechanisms are involved in the central actions of potassium and these central mechanisms may contribute to the salutary effects of a potassium-rich diet in hypertensive subjects. The present studies demonstrate a potentially important relationship between Na+,K+-ATPase activity in the central nervous system and neural regulation of arterial blood pressure

ISSN:0263-6352    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

We studied the effects of endothelin on angiotensin converting enzyme (ACE) in cultured pulmonary artery endothelial cells. ACE activity was increased 2.5-fold by the addition of 1 × 10-8mol/l endothelin-1. Endothelin-1 also stimulated calcium influx and phospholipase C activity in a dose-dependent manner. Calcium influx, phospholipase C and ACE activity were suppressed 60–70% in the presence of endothelin-1 (110to 10-6mol/l) by 50 μl neomycin. These results suggest that ACE was stimulated by endothelin-1 and that its activity may be closely related to phosphatidylinositol turnover stimulated by endothelin-1.

ISSN:0263-6352    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

To investigate the role of calcitonin gene-related peptide (CCRP) in blood pressure regulation, we used rats with hypertension, induced by the chronic infusion of norepinephrine or angiotensin II, and examined changes in the systemic hemodynamics using the radioactive microspheres method. CGRP (0.05 μg/kg per min) administered simultaneously with norepinephrine (1.8mg/kg per day) significantly reduced the systolic blood pressure of conscious rats compared with norepinephrine infusion alone. Similarly CCRP given with angiotensin II (0.9mg/kg per day) significantly reduced the systolic blood pressure compared with angiotensin II alone. The antihypertensive effect of CGRP was sustained for 6 days. CCRP infusion decreased the total peripheral resistance but caused no change in cardiac output compared with rats given only pressor substances. Thus, a subdepressor dose of CGRP can modulate the vasopressor effects of norepinephrine and angiotensin II. CCRP may be involved in the regulation of blood pressure via an effect on peripheral vascular resistance

ISSN:0263-6352    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The relationship between sodium intake and blood pressure in adolescents was examined in a dietary intervention study. One hundred schoolchildren aged 11-14 years and representing the top, middle and bottom deciles of the blood pressure range completed a crossover protocol requiring them to raise and lower their sodium intake for alternate periods of 4 weeks. Blood pressure and urinary sodium excretion were assessed weekly and diet diaries were recorded at the end of each 4-week diet period. Diet-diary analysis confirmed that sodium intake was selectively affected by the intervention. Estimates of average urinary sodium excretion at the end of each diet period differed by more than 80 mmol/day. However, there was no significant change of either systolic or diastolic blood pressure, measured supine in the whole study group, in either sex or in any of the sub-groups, even in those children representing the highest blood pressure decile. Furthermore, the blood pressure changes seen in individuals during the crossover did not correlate with their changes in sodium excretion. This lack of effect of sodium on blood pressure is consistent with other dietary intervention studies in children and supports the hypothesis that the sodium sensitivity of blood pressure is age-related. We conclude that dietary sodium restriction alone has little potential for lowering blood pressure at an early age, even in children with higher than average blood pressure

ISSN:0263-6352    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

To investigate the molecular mechanism of sustained hypertension in two-kidney, one clip (2K1C) hypertensive rats, possible changes in renin gene expression in the kidney and angiotensinogen in the liver were studied. In 2K1C rats 4 weeks after clipping, the plasma renin and angiotensin II levels were significantly higher than those in sham-operated rats, but the plasma angiotensinogen levels were similar in the two groups. At this time, expression of the renin gene in the ischaemic kidney of 2K1C rats was 2.6-times that in sham-operated rats (P<0.05), but expressions of the angiotensinogen gene were similar in the two groups. Sixteen weeks after clipping, the plasma renin and angiotensin II levels in 2K1C rats were not significantly higher than those in sham-operated controls, but expression of the renin gene in the kidney was still 2.2-times higher in 2K1C rats than in controls (P<0.05). The plasma angiotensinogen level was significantly higher in 2K1C rats than in controls (P<0.05), and expression of the angiotensinogen gene in the liver was 2.9-times higher in 2K1C rats than in controls (P<0.01). These results indicate that the roles of the renin-angiotensin system in maintenance of hypertension in 2K1C rats differ in the acute and chronic phases: in the acute phase, over-expression of the renal renin gene coupled to increased renin secretion plays the major role in elevating the blood pressure; in the chronic phase, a counter-regulatory mechanism may affect the post-transcriptional fate of renin. Consistent over-expression of the renin gene and mobilization of the angiotensinogen gene, i.e. over-expression of the renin-angiotensin system, may contribute to the maintenance of hypertension

ISSN:0263-6352    

出版商:OVID    

年代:1991

数据来源: OVID