ISSN:0263-6352    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Vascular noradrenergic transmission and the effect of captopril on this transmission were examined in the blood perfused rat mesenteric vasculature in situ during the development of two-kidney, one clip Goldblatt hypertension. Three groups of rats including sham operated, 6-8 day hypertensive and 4-6 week hypertensive were studied. Mean blood pressures during anaesthesia were 90.0 ± 2.0, 119.7 ± 4.7 and 131.8 ± 6.8 mmHg in the three groups, respectively. Mesenteric vasoconstrictor responses to norepinephrine were significantly potentiated in both of the hypertensive groups relative to the sham group. Mesenteric vasoconstrictor responses to nerve stimulation were similar in the sham and 6-8 day hypertensive groups. However, responses to nerve stimulation were significantly potentiated in the 4-6 week hypertensive group relative to the sham group. Captopril (1 mg/kg, i.v.) lowered mean blood pressure in all groups, equalizing blood pressure in the 6-8 day hypertensive and sham groups. However, the blood pressure in the 4-6 week hypertensive rats remained significantly elevated after 1 mg/kg captopril. An additional dose of captopril did not lower blood pressure further in this group. Mesenteric vasoconstrictor responses to nerve stimulation and norepinephrine in the three groups were minimally affected by captopril, with significant differences between control and captopril-treated responses occurring randomly at a point or two in a dose-response or frequency-response curve for a given group. The differences in vascular responsiveness to nerve stimulation and norepinephrine between the hypertensive and sham groups continued to be evident after captopril. In conclusion, although changes in vascular noradrenergic transmission occur during the development of two-kidney, one clip Goldblatt hypertension, it appears that facilitation of noradrenergic transmission by angiotensin II does not contribute to these changes in the rat mesentery.

ISSN:0263-6352    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

A double-blind placebo-controlled study was carried out in 10 sodium-deplete normal men to determine whether prostaglandin synthesis inhibition (PG-inhibition) by indomethacin (150 mg daily for three days plus an additional 50 mg on the morning of the active experiments) affected blood pressure and humoral factors at exercise. Urinary sodium excretion during placebo averaged 39 mEq/24 h.Independent of the level of physical activity, PG-inhibition increased (ρ<0.001) intra-arterial systolic pressure by 12 mmHg and mean and diastolic pressure by 5 and 3 mmHg, respectively. Heart rate, body weight and exercise capacity were not significantly changed.Following PG-inhibition plasma 13,14-dihydro-15-keto-prostaglandin Fα, plasma renin, angiotensin II and aldosterone were reduced (ρ<0.001) to a similar degree at rest and exercise. However, PG-inhibition did not abolish the exercise related stimulation of the plasma renin-angiotensin-aldosterone system. PG-inhibition had no significant effect on the plasma catecholamines nor on the urinary excretion of aldosterone and kallikrein. Twenty-four-h urinary sodium (—15 mEq; ρ<0.01) decreased.In sodium-deplete subjects prostaglandins seem to exert a depressor action on the systemic circulation, and to have a tonic influence on the renin system. Both these effects are similar at rest and exercise. Prostaglandins are probably not involved in the exerciseinduced stimulation of the plasma renin-angiotensin-aldosterone system.

ISSN:0263-6352    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Responses to mental stress [a colour word test (CWT), orthostatic testing (ORT) and a cold pressor test (CPT) were studied in 33 subjects with essential hypertension (EHT), 16 subjects with borderline hypertension (BHT) and 17 age and sex-matched normotensive controls (NT). Venous plasma noradrenaline (NA) was similar in all groups. CWT induced marked circulatory responses and metabolic activation with minor increases in NA. Circulatory and NA responses to ORT and CPT were similar in all groups. CWT elevated diastolic blood pressure more in BHT and tended to elevate HR more in EHT and BHT than in NT. Plasma adrenaline (ADR) tended to be higher in BHT and increased during all provocations in EHT and BHT but not in NT. Early hypertension appears to be associated with enhanced cardiovascular and sympatho-adrenal reactivity (resembling a hypothalamic defence reaction) which is revealed by mental stress, rather than stimuli such as ORT or CPT. Venous plasma NA has limitations in defining neurogenic alterations in hypertension since it reflects poorly sympathetic activity in the organs responsible for pressor responses to emotional stimuli. Plasma ADR is more valuable in this respect.

ISSN:0263-6352    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

This study examines the influence of bromocriptine, a dopamine agonist, on circadian secretory patterns of plasma 18-hydroxycorticosterone (18-OHB) and cortisol in essential hypertension. Patients with sustained essential hypertension were studied after they had reached equilibrium on a constant 150 mmol sodium and 80 mmol potassium intake. Plasma 18-OHB and cortisol determinations were made at 30-min intervals over 24 h during a control and bromocriptine treatment period (bromocriptine, 2.5 mg t.i.d. for five days). Circadian patterns for plasma 18-OHB and cortisol were observed in all patients before and after bromocriptine. Although bromocriptine did not affect the circadian rhythm of 18-OHB and cortisol it did decrease mean 24-h recumbent 18-OHB from 23 +42.2 to 14.3 ± 1.4 ng/dl. These results suggest that there is a circadian rhythm of both 18-OHB and cortisol secretion in patients with essential hypertension as in normotensives. Dopaminergic mechanisms exert an effect on the quantitative secretion of 18-OHB. However, the circadian rhythm for 18-OHB and cortisol does not appear to be dependent on dopaminergic mechanisms.

ISSN:0263-6352    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

High school students who had at least one parent with hypertension (n =22) were compared to schoolmates of the same age with a negative family history of hypertension in the parents (n =21). We investigated in both groups the maximal rate of the ouabainsensitive Na pump and the Na-K cotransport in nystatin-loaded cells and the Lii-Naocountertransport in lithium-loaded cells. The two groups were significantly different only in the sum of net Na transport mediated by the Na-K pump and Na-K cotransport. The mean diastolic blood pressure in the positive family history group was significantly higher. With control for blood pressure the difference in the maximal rate of Na transport was no longer significant; it remains uncertain if control for blood pressure represents 'over-adjustment'. The finding of a higher maximal rate of Na transport in these adolescents who are at increased risk of future hypertension, yet currently well within the normal range, suggests that abnormal sodium metabolism may be a useful marker and appears early in the pathogenesis of this disease.

ISSN:0263-6352    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The responses to 48 h of renal artery stenosis were compared in uninephrectomized, chronically-instrumented dogs with or without inhibition of angiotensin II (All) formation by enalapril. Mean arterial pressure rose by an average of 29.9 mmHg (s.e.m. 3.5) in untreated dogs and by 14.5 mmHg (s.e.m. 2.8) in enalapril-treated dogs over the two days of stenosis. Renal artery stenosis reduced glomerular filtration rate (GFR) by 49% (s.e.m. 9) in untreated dogs and by 86% (s.e.m. 8) in enalapril-treated dogs. Compared to untreated dogs, enalapril-treated dogs also had lower renal artery pressure distal to the stenosis, drank less water and had larger rises in plasma K+following renal artery stenosis. There were no differences in renal blood flow or urinary Na+excretion in the two groups of dogs. Thus blockade of All production did not prevent hypertension occurring in response to renal artery stenosis, but the rise in blood pressure was only about half that which occurred in normal dogs and GFR was much more severely reduced.

ISSN:0263-6352    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Fifteen males with previously untreated essential hypertension in WHO stage I, aged 20- 64 years were studied on an outpatient basis. Oxygen consumption, heart rate, cardiac output (Cardiogreen) and intra-arterial brachial pressure were recorded at rest in a supine and sitting position and during steady state work at 50, 100 and 150 W.Following the haemodynamic study, nifedipine (long-acting form) 40-80 mg daily was given as the sole drug for 3-12 months (mean 11 months) whereupon the haemodynamic study was repeated. Systolic, diastolic and mean arterial pressures fell about 17% at rest supine and sitting and from 15 to 10% at the three different workloads (P<0.001). All but one patient demonstrated a fall in mean arterial pressure of 10 mmHg or more. The fall in pressure was associated with a statistically significant (P<0.05) reduction in total peripheral resistance (17% during rest and 10 to 16% during exercise). There were no statistically significant changes in oxygen consumption, heart rate, cardiac index or stroke index.

ISSN:0263-6352    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The effect of local infusion of ouabain into the forearm vascular bed has been examined in 15 normotensive male volunteers in an attempt to define the nature of the functional abnormalities of the resistance vessels in primary hypertension. Ouabain and other drugs were infused into the brachial artery and forearm blood flow was measured by venous occlusion plethysmography. Infusion of ouabain at 2 μg/min for 1 h caused a 26% reduction in forearm blood flow with a small rise in systemic arterial pressure; the increase in vascular resistance was unaffected by prior treatment with phentolamine. After infusion of ouabain the dilator response to potassium was reduced by 33% but the responses to verapamil and sodium nitroprusside were unchanged. The results show that acute depression of sodium pump activity by ouabain reproduces the increased resting resistance and impaired response to potassium that are seen in hypertension. It does not reproduce the relative enhancement of responsiveness to verapamil that is also observed in the resistance vessels of patients with hypertension and this abnormality must have some other cause.

ISSN:0263-6352    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Free intracellular calcium [Ca2+]i, sodium [Na+]iand potassium [K+]iwere assessed in freeze-thawed human red blood cells (RBC) by ion-selective electrodes.After metabolic depletion by 30 mM 2-desoxy-glucose, [Ca2+]iincreased faster and to significantly higher values in RBC from 16 patients with mild to moderate essential hypertension (mean diastolic blood pressure 111 ±10 mmHg) than in the RBC of 24 normotensives. The rate of [Ca2+]iincrease was 7.0 ± 3.6 versus 3.7 ± 4.0 μmol/h/l cells (P<0.01) for the first 24 h and 8.1 ±4.8 versus 6.4 ± 3.5 μmol/h/l cells for the following 24 h. [Na+]ibefore and after 24 h incubation was significantly higher in hypertensives, whereas basal [Ca2+]iand [K+]ibefore and after incubation were the same in both groups. After Ca loading by ionophore A 23187, the maximum rate of [Ca2+]iextrusion was not significantly lower in intact RBC from hypertensives than in those from normotensives (59.5 ±7.8 versus 87.9 ±18.1 μmol/min/l cells).These results indicate disturbances in RBC Ca metabolism similar to those observed earlier for Na and K. If generalized, the defect could lead to raised [Ca2+]iin smooth muscle and sympathetic nerve tissue, thus causing increased vascular tone and probably catecholamine release with subsequent arterial hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1983

数据来源: OVID