ISSN:0263-6352    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Angiotensin converting enzyme (ACE) activity was measured by fluorimetry in the plasma, lung, heart, aorta and kidney (cortex and medulla) of 3-, 5-, 8- and 11-week-old spontaneously hypertensive rats (SHR) and compared with that of age-matched Wistar—Kyoto rats (WKY). In the plasma, lung and kidney (cortex and medulla), ACE activity was lower in SHR than in WKY. This was evident as early as the age of 3 weeks. In contrast, there were no differences between SHR and WKY in the aorta and the heart. Age-related variations in ACE activities differed in each tissue and in both groups of rats, but no major modifications were correlated with the development of hypertension. A binding assay was performed with [3H]ramiprilat; affinity (KD) and the maximum number of binding sites (Bmax) were determined in plasma and tissues of 3-week-old SHR and WKY. The KD values were identical in the two groups but Bmax was lower in all SHR tissues except in the heart; these results might be related to the decrease in ACE activity. Our results probably reflect genetic differences in ACE activity between SHR and WKY, and suggest that ACE regulatory mechanisms act differently in each tissue.

ISSN:0263-6352    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

We studied neural influences on the renal actions of atrial peptides in anaesthetized cats by comparing the response to atrial natriuretic factor (ANF) infusion in the innervated kidney and in the contralateral surgically denervated kidney. During ANF infusion arterial pressure decreased, the heart rate did not change and blood flow to both kidneys increased slightly. Vascular conductances became slightly but significantly higher in the denervated kidneys than in the controls. In both kidneys, the glomerular filtration rate increased transiently and significantly. Inhibition of renin release was more prompt and larger in the innervated than in the denervated kidneys. ANF infusion caused a significant increase in sodium and water excretion from both the innervated and denervated kidneys. However, the diuretic and natriuretic effect in the innervated kidneys, although proportionally greater than that in the denervated kidneys, was of shorter duration and subsided after 20min of ANF infusion. Efferent renal nerve activity did not change during the initial 10 min of ANF infusion but thereafter increased progressively and significantly. We conclude that the effects of atrial peptides on renin release and excretory functions are influenced by renal nerve activity.

ISSN:0263-6352    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Plasma viscosity and fibrinogen concentrations were measured in 70 diabetics (35 hypertensive and 35 normotensive) and compared with those of 35 age- and sex-matched normotensive healthy subjects in relation to body weight. The body weight, body mass index, blood pressure (systolic and diastolic), mean arterial pressure, plasma viscosity and fibrinogen level of the hypertensive diabetics were significantly higher than the values seen in the controls. Among the normotensive diabetics, only the fibrinogen concentration was elevated above that of the controls (P<0.01). Body weight, body mass index, blood pressure (systolic and diastolic), mean arterial pressure and plasma viscosity were all significantly higher in the hypertensive diabetics than in their normotensive counterparts. The difference in fibrinogen titre of both groups of diabetics was not significant. Body mass index, fibrinogen and plasma viscosity were correlated significantly with systolic and diastolic blood pressures (P<0.001). The order of relative contribution showed that fibrinogen contributed most to blood pressure, followed by plasma viscosity and then body mass index. The results suggest that high levels of body weight, fibrinogen concentration and plasma viscosity could contribute to the development of hypertension in diabetic Nigerians.

ISSN:0263-6352    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

We describe here a method of measuring angiotensin peptides and their carboxy-truncated metabolites in human plasma using N-terminal-directed antisera. Antisera raised against N-acetylated angiotensin (Ang) II and N-acetylated Ang III analogues were used to develop two radioimmunoassays. Extracted plasma samples were acetylated prior to separation of cross-reacting angiotensin peptides by high-performance liquid chromatography (HPLC). Fractions were assayed with both antisera to obtain measurements for eight angiotensin peptides. Angiotensin levels measured in normal males were (fmol/ml plasma, means ± s.e.m., n=14): Ang-(1—7) 1.0 ± 0.2, Ang II 13.9 ±2.0, Ang-(1-9) 7lt;0.4, Ang I 19.5 ± 2.4, Ang-(2-7) <1.1, Ang III 2.9 ± 1.0, Ang-(2-9) <2.1, Ang-(2-10) 2.4 ± 0.8. Hypertensive patients receiving angiotensin converting enzyme (ACE) inhibitor therapy (n=8) had an increase in Angt to 187.3 ± 107.2fmol/ml (P=0.002), and a reduction in Angll to 4.8 ± 1.2fmol/ml (P<0.001). Furthermore, these patients showed a ninefold increase in Ang-(1—7) to 9.7 ± 4.3 fmol/ml (P<0.001), indicating a role for prolylendopeptidase in the metabolism of Ang I in vivo. These N-terminal assays have demonstrated that carboxy-truncated metabolites of Ang I and Angll make little contribution to plasma angiotensin peptides, except during ACE inhibitor therapy. Furthermore, these antisera allow the measurement of Ang I and Angll in the same radioimmunoassay of fractions from HPLC, providing a highly reliable estimate of the Angll: Ang I ratio.

ISSN:0263-6352    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Endothelin is a novel endothelium-derived vasoconstrictor peptide. We investigated its effect on atrial natriuretic factor (ANF) release and on several cardiovascular and renal parameters, since ANF release is induced via hemodynamic changes in response to angiotensin II, another vasoconstrictor peptide. Male Sprague-Dawley rats were infused intravenously for 60min with either saline or endothelin at 10, 50 or 100ng/kg per min and then allowed to recover for 20 min. A third group was splenectomized 24 h before infusion with 100ng/kg per min endothelin. Mean arterial, left ventricular end-diastolic and central venous pressures (dP/dtmax), heart rate, plasma ANF-(1-98) concentration, urinary volume, urinary sodium excretion and hematocrit were evaluated. Mean arterial pressure was elevated by both medium and high endothelin doses, and with the high dose this elevation was sustained beyond the infusion period. No increases in either left ventricular end-diastolic or central venous pressures were observed at any dose level. In fact, in rats infused with 100 ng endothelin there was a progressive decline in central venous pressure and a raised hematocrit, even in the splenectomized group, suggesting a loss of plasma volume. All three dose levels elevated the dP/dtmax at different infusion times. The heart rate was not modified by any endothelin dose. Despite the decreased central venous pressure and unaltered left ventricular end-diastolic pressure, the 100ng/kg per min endothelin infusion induced a threefold increase in plasma ANF levels; these were correlated with changes in the dP/dtmax (r=0.49, P<0.05). Both 50 and 100ng/kg per min endothelin produced a decline in urinary volume and urinary sodium excretion, but this was significant only at the higher dose. The non-pressor dose of endothelin (10ng/kg per min) tended to increase diuresis, and significantly enhanced natriuresis. We conclude that increases in ANF induced by endothelin are not mediated by changes in atrial pressure, but could be evoked either by a direct stimulatory effect on cardiocytes or by increased cardiac contractility. Also, the possible role of impaired renal function induced by the higher dose of endothelin cannot be disregarded. The natriuretic response to low endothelin doses could be secondary to a vasodilatory action of the peptide on the renal vasculature

ISSN:0263-6352    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The temporal blood pressure course and the diurnal profile of the renin–angiotensin system were examined in 13 patients with essential hypertension receiving hydrochlorothiazide and enalapril once daily. Blood samples were taken and blood pressure was measured before the habitual morning dose of hydrochlorothiazide and enalapril (at 8.00 a.m.) and at seven time points over the next 24 h. During the period of maximal effect of enalapril (from 11.00 a.m. to 2.00 p.m.), the increase in plasma renin concentration ranged from no change to an 800% increase. A negative correlation was observed between an increase in plasma renin and a decrease in immunoreactive plasma angiotensin II concentration (Spearman rank-order correlation coefficient=0.83). Notably, the greatest changes in plasma renin and angiotensin II concentrations after enalapril were seen in those patients whose blood pressure fell most during the day. We conclude that hypertensive patients on long-term therapy with enalapril once daily vary widely in their between-dose biochemical response to the drug, and that there is a significant association between the responsiveness of the plasma renin–angiotensin system and the effect on 24 h blood pressure.

ISSN:0263-6352    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Increased vascular resistance in spontaneous hypertension has been attributed to a reduced arteriolar lumen and a decrease in the number of arterioles and capillaries. In the present study, microvascular mechanisms for increased resistance were investigated in the cremaster muscle of 5-6-week-old spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto rats (WKY) using intravital microscopy. Vessels were classified on the basis of their location in the network relative to their branching order and function (A1—A4). In each preparation, one vessel of each category was observed for its side-branches, using bright-field microscopy. By comparing the number of side-branches seen under control conditions and after maximal vasodilatation (10~3mol/l adenosine, topically) we assessed their functional reserve. Capillary density was investigated using incident fluorescence microscopy. Both under control conditions and after vasodilatation, mean arterial pressure and heart rate were increased in SHR (mean arterial pressure: SHR 103±4mmHg, WKY 89 ± 3mmHg, P<0.05; heart rate: SHR 380 ± 16 beats/min, WKY 343 ± 12 beats/min, P<0.05). Arterioles (A1-A4) of SHR and WKY were equal in diameter (SHR: 75.8 ± 3.2, 48.7 ± 1.1, 21.4 ± 0.9, 10.0 ± 0.04 ^m; WKY: 71.6 ± 2.4, 48.9 ± 1.1, 18.5 ± 0.9, 9.8 ± 0.3 urn; A1-A4, respectively). After adenosine, the relative increase in diameter was similar in both groups. The number of side-branches under control conditions was similar in A1 and A2 vessels. SHR had fewer A3 vessels per A2 and fewer A4 vessels per A3 (per unit length), indicating a diminished arteriolar reserve. SHR capillary density was lower under control conditions (SHR 33.1 ± 1.2 mm/mm2; WKY 44.9 ± 1.7 mm/mm2; P<0.05). No capillary recruitment occurred during adenosine administration. We conclude that, in the early phase of spontaneous hypertension, a structurally diminished functional arteriolar reserve and a reduced capillary density, rather than a decreased dilating capacity or a reduced vessel lumen, are the primary mechanisms leading to the increased vascular resistance in cremaster muscle.

ISSN:0263-6352    

出版商:OVID    

年代:1990

数据来源: OVID