ISSN:0263-6352    

出版商:OVID    

年代:1988

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Enkephalins, endogenous opioid pentapeptides, are found in normal chromaffin tissue and may influence blood pressure regulation. We studied the subcellular localization and precursor-product status of enkephalin immunoreactivity in 11 human phaeochromocytomas (seven adrenal, four extra-adrenal). Enkephalin immunoreactivity was found in all phaeochromocytomas, it paralleled radio-immunoassay standard curves and was not destroyed by boiling or protease inhibitors i.e. ethylenediaminetetraacetic acid (EDTA) and phenylmethylsulfonyl fluoride (PMSF). Sucrose gradients localized enkephalin immunoreactivity to chromaffin granules (55 ± 17% of total immunoreactivity; n=6).In vitrogranule lysis released 81% of the enkephalins and 91% of the catecholamines. Thus, phaeochromocytoma enkephalins are present in the soluble core of chromaffin granules, along with catecholamines. Enkephalin immunoreactivity was not contained in purified chromogranin A, either before or after trypsin cleavage. High pressure liquid chromatography (HPLC) elution of enkephalin immunoreactivity matched that of synthetic methionine-enkephalin, leucine-enkephalin, and methionine-sulfoxide-enkephalin standards. Enkephalin immunoreactivity was augmented by trypsin alone and by trypsin plus carboxypeptidase B (by 352 ±56%), suggesting that the majority of the enkephalins were present in higher molecular weight precursor form. Sephacryl S-200 gel filtration of chromaffin granule lysate revealed a trypsinaugmented putative human enkephalin precursor with a molecular weight of 2000-4000 daltons as well as product enkephalins. Enkephalin concentration in phaeochromocytoma closely paralleled the epinephrine, but not the norepinephrine content of the tumours. However, it was not statistically different in adrenal versus extra-adrenal tumours. Thus, these peptides are contained in high molecular weight form in the soluble core of catecholamine storage vesicles, predominantly epinephrine vesicles

ISSN:0263-6352    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The effect of vanadate, an agent that in rats exerts potent vasoconstrictor and diuretic action on blood pressure, cardiac output, total peripheral resistance and plasma and extracellular fluid volume, was investigated in normal rats and in rats with diminished renal excretory function. In normal rats, chronic dietary vanadate did not affect blood pressure, but induced an increase in total peripheral resistance and a decrease in cardiac output, plasma and extracellular fluid volume. In rats with diminished renal excretory function, vanadate increased blood pressure and total peripheral resistance without affecting cardiac output, plasma and extracellular fluid volume. The results indicate that this agent, with predominant vasoconstrictor action, does not cause sustained hypertension unless renal excretory function is diminished

ISSN:0263-6352    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

We have re-examined digoxin-like immunoreactivity, commonly detected in plasma with antibodies, in order to determine whether it could represent the putative natriuretic factor originally proposed by de Wardener and Clarkson [1]. Experiments were conducted in adult rabbits with two-kidney, two wrapped hypertension and in shamoperated controls. Six weeks after the bilateral renal cellophane wrapping or sham operation, the mean arterial pressure (MAP) was approximately 40 mmHg higher in the wrapped group. At this time the rabbits started a low-, normal- or high-salt diet (1.6, 25.6 and 40.8 mmol Na+/100 g) which continued for 2 weeks. During the final 3 days urinary volume and total sodium content measured in 24-h collections was significantly lowered in the rabbits on the low-salt diet and increased by the high-salt diet (P< 0.01 for both). This pattern was identical for the normotensive and renal hypertensive rabbits. Digoxin-like immunoreactivity was measured at the beginning and at the end of the 2-week period of the salt study. Immediately before commencing the various salt diets the digoxin-like immunoreactivity, measured as ng digoxin equivalents/ml, was only marginally elevated in the renal hypertensive compared to the normotensive animals (it averaged 94.7 ± 7.7 and 80.9 ± 5.9 ng digoxin equivalents/ml, respectively). Neither the low- nor the high-sodium diet affected plasma digoxin-like immunoreactivity in either the normotensive or the renal hypertensive animals (P> 0.10). These results indicate that digoxin-like immunoreactivity is present in the plasma of normotensive and renal hypertensive rabbits. The lack of effect of alterations in dietary sodium intake, particularly in the renal hypertensive group (a model of hypertension with impaired renal function), indicates that the digoxin-like immunoreactivity may not represent the putative natriuretic hormone

ISSN:0263-6352    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

In order to understand the regulation of vascular vasopressin receptors in hypertension, vasopressin (AVP) binding sites and the pressor response to AVP in the perfused mesenteric vasculature of DOCA-salt hypertensive rats, sodium-loaded and DOCAtreated rats were investigated. The binding capacity for AVP (Bmax) was significantly reduced (P< 0.05) in uninephrectomized, DOCA-treated rats (70 ± 17fmol/mg protein) and in DOCA-salt hypertensive rats (90 ± 9 fmol/mg protein) with respect to uninephrectomized rats (130 ± 32 fmol/mg protein) or uninephrectomized salt-loaded rats (155 ± 47 fmol/mg protein), with no change in affinity. In these rats with lower receptor density, however, the maximal pressor response to AVP in the perfused mesenteric vascular bed was increased (P< 0.05). In DOCA-salt hypertensive rats plasma AVP was higher than in the other groups. In similarly treated rats with intact kidneys, which therefore did not become hypertensive, receptor density was significantly decreased after combined DOCA-salt treatment, together with an exaggerated pressor response to AVP and increased plasma AVP concentrations. These results suggest that AVP receptors are down-regulated when there is an increment in the plasma concentration of AVP, although other factors may also play a role. Biological responses to AVP are, however, increased in spite of decreased receptor density and this phenomenon is independent of the elevation in blood pressure and results from an exaggerated response mediated by post-receptor mechanisms

ISSN:0263-6352    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

During low-dose adrenaline infusion, platelet count, platelet size, plasma ß-thromboglobulin (BTG) and forearm vascular resistance (FVR) were measured in twelve 40-year-old men with mild, untreated hypertension. The average platelet count increased from 195 to 226 x 109/l (P< 0.001), platelet size from 7.31 to 7.53 x 10-15/l (P< 0.01), BTG from 0.61 to 1.08 nmol/l (P< 0.02) and FVR decreased from 97 to 58 (arbitrary units;P< 0.001) during the infusion. The change in platelet count reflects splenic release of platelets, the change in plasma BTG reflects platelet release reaction, while the reduced FVR reflects vascular smooth muscle cell relaxation. In 11 normotensive men aged 40 years, platelet count increased from 187 to 201 x 10g/l (P< 0.01) during an equal low-dose adrenaline infusion. This increase in platelet count is significantly less than in the hypertensive group (P< 0.01). There was statistically no significant change in platelet size, BTG or FVR in the normotensive group. Arterial adrenaline rose from 0.5 to 2.5 nmol/l in the hypertensive and from 0.5 to 2.4 nmol/l in the normotensive group. A third group of 12 normotensive men received saline infusion: neither platelet parameters nor FVR changed in this group. Thus, a small and equal dose of adrenaline elicited a greater increase in platelet count, an enhanced platelet release reaction and a more pronounced forearm vasodilation in hypertensive than in normotensive subjects

ISSN:0263-6352    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

This study focuses on the relationship between some aspects of intra-erythrocytic sodium metabolism (intra-erythrocytic Na content, Na.Li-countertransport), blood pressure, and family history of hypertension, in a group of 84 randomly selected school children (45 males, 39 females). Na,Li-countertransport was significantly related to both systolic blood pressure (SBP) and diastolic blood pressure (DBP) only in boys at the univariate level, but both of these associations lost statistical significance after the possible confounding role of weight and height were taken into consideration. In both sexes, participants with a family history of hypertension had similar values of both intra-erythrocytic Na content and Na,Li-countertransport to participants with no family history.We conclude that family history of hypertension does not seem to play an important role in the determination of either intra-erythrocytic Na content or Na,Li-countertransport at this age. Although the positive association between Na,Li-countertransport and blood pressure observed in adult males is already present in childhood, this probably is still, at least in part, dependent upon body size

ISSN:0263-6352    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Enhanced renal vasoconstriction and renal tubular sodium reabsorption mediated by noradrenaline and angiotensin II (Ang II) have been implicated in the pathogenesis of essential hypertension. Since these effects seem to be calcium-dependent, renal haemodynamic and tubular function were studied following acute and long-term treatment with the calcium antagonist felodipine in 10 patients with essential hypertension.After acute felodipine administration mean blood pressure (MBP) decreased (from 111 to 95 mmHg;P< 0.01), renal blood flow (RBF), estimated from hippurate clearance, increased (from 1030 to 1175ml/min;P< 0.01) and glomerular filtration rate (GFR) was unchanged (109 versus 112ml/min). Fractional excretion (FE) of sodium, potassium, calcium, magnesium, chloride, bicarbonate and urate increased for 12 h. Following long-term felodipine treatment, mean blood pressure was reduced (97 mmHg;P< 0.01) and RBF and GFR were unchanged (1032 and 114ml/min, respectively). Fractional excretion of urate and calcium was increased for 24 h (from 5.9 to 6.9%;P< 0.05 and from 1.1 to 1.3%;P< 0.05, respectively). Serum urate decreased (from 377 to 347 µmol/l;P< 0.01) whereas serum calcium was unchanged. Fractional excretion of sodium, potassium and chloride was increased between 3 and 6 h after felodipineThe renal haemodynamic findings after acute felodipine administration are indicative of a direct renal vasodilator action of felodipine which augments the autoregulatory renal vasodilation to produce an overall increase in RBF. Since GFR was unchanged, the increased renal excretion of electrolytes and urate reflects an action at the tubular level. Following long-term felodipine administration autoregulatory adjustment of RBF predominated

ISSN:0263-6352    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The purpose of this study was to compare in the individual hypertensive patient the blood pressure lowering effect of β-blocking agent i.e. betaxolol with that of a calcium entry blocker, i.e. verapamil. The antihypertensive efficacy of the drugs was evaluated both at the physician's office and by monitoring ambulatory daytime blood pressure using a portable blood pressure recorder (Remler M2000). Seventeen patients with uncomplicated essential hypertension (aged 35-67 years) were treated for two consecutive 6-week periods with either betaxolol, 20 mg/day or a slow-release formulation of verapamil, 240-480mg/day. The sequence of treatment phases was randomly allocated and a 2-week wash-out period preceded each treatment. Both betaxolol and verapamil had a significant blood pressure lowering effect when assessed at the physician's office. However, ambulatory recorded blood pressures were significantly reduced only with betaxolol. In the presence of a physician, the best responders to betaxolol tended to be also the best responders to verapamil, whereas there was no relationship between the fall in ambulatory recorded blood pressure observed during betaxolol and the corresponding fall during verapamil administration. The blood pressure response to both betaxolol and verapamil was not related to age

ISSN:0263-6352    

出版商:OVID    

年代:1988

数据来源: OVID