ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

We studied the function of the cardiac sympathetic nerve varicosity in isolated right atrial preparations of spontaneously hypertensive rats (SHR) and Wistar- Kyoto (WKY) rats at 4, 9, 14, 20 and 50 weeks of age. Cumulative concentration-atrial period response (C-R) curves to isoprenaline showed similar maximum response and sensitivity (EC50) at all ages but there was an age-related fall in resting atrial rate. Similar results were found for methoxamine (α1- aradrenoceptor agonist) although the maximum response was significantly less than for isoprenaline. The time-dependent recovery (T1/2) of the fall in atrial period in response to sympathetic nerve stimulation from electrical field pulses (1-32 at 1 Hz) was enhanced by neuronal uptake inhibition by desipramine (0.1-1 µmol/l), to a similar degree at all ages. Pre-junctional α2- adrenoceptor stimulation by clonidine caused progressively more inhibition of the number of field pulses-fall in period relationship with age. SHR atria were similar to WKY rat atria at all ages except for a further impairment of the development of pre-junctional α2- adrenoceptors. These studies indicate that the function of the cardiac sympathetic varicosity matures early (by 4 weeks) and overall there is very little impairment in SHR versus WKY rat atria.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The distribution of blood pressure and associated factors (height, weight, body mass index, age, social class) was assessed in young Mexican adults, with a cross-sectional study of 657 male and female students enrolled at the University of Mexico, aged from 19 to 25 years. Significantly higher blood pressure levels were observed in males than in females. Borderline hypertension was found in 20.7% of the study subjects. Of all anthropometric factors, age and social class, weight was determined by stepwise regression analysis as the best predictor for blood pressure when using a linear model. However, when a quadratic model was used, a 'U' relationship and a significant variation between blood pressure and social class was detected. This relationship was magnified when blood pressure was categorized into borderline hypertension and normotensives. These findings suggest the hypothesis that hypertension has a non-linear association with social class in environments that are undergoing an intermediate step of modernization and economic transition such as is occurring in Latin American countries today.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Unclipping the Goldblatt hypertensive rat lowers the blood pressure by cells in the renal papilla, the renomedullary interstitial cells (RIC), secreting a hormone that is part of a vasodilator system. A vasodilator, termed medullipin I, can be extracted from the renal papilla. Medullipin I and the renal venous effluent following unclipping have identical biologic properties. Medullipin I appears to be the agent secreted by the kidney following unclipping. Both medullipin I and the renal venous effluent must traverse the liver to be active. Medullipin I is converted in the liver to its active form, medullipin II. The blood pressure-lowering effect of both medullipin I and the renal venous effluent after unclipping are blocked by SKF 525A, the inhibitor of cytochrome P- 450. The relation of the kidney to the liver was tested using the rate of decline of the blood pressure after unclipping as an index of the endocrine antihypertensive function of the kidney − acceleration of the decline being considered as increased function, decrease of the decline as decreased function. Five compounds: BW755C, phenobarbital, ketoconazole, eicosatetraynoic acid (ETYA) and butylated hydroxytoluene (BHT), and two manipulations: uretero-caval anastomosis (UCA) and removal of the liver from the circulation were used followed by unclipping. BW755C, inhibitor of both cyclo-oxygenase and lipoxygenase, potentiated the antihypertensive function to a maximum. It is reasoned that inhibition of the first two pathways of arachidonic acid metabolism potentiates the third pathway, the cytochrome P−450 pathway. BW755C and phenobarbital maintained their potentiation after UCA indicating that their action is not mediated by volume loss. Both lost their effect when the liver was removed from the circulation indicating the necessity of the hepatic action. Inhibitors of cytochrome P-450, ketoconazole and ETYA, prevented the decline of the blood pressure after unclipping indicating an involvement of cytochrome P-450-dependent system. BHT blocked the decline of the blood pressure after unclipping supporting the existence of an oxidative step in the activation of medullipin I to medullipin. II. Medullipin I could be a product of arachidonic acid metabolism that is converted to medullipin II by the cytochrome P-450-dependent enzyme system of the liver.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

A new technique to permit gradual changes in atrial distension has been developed in an isolated perfused rabbit atrium preparation. Graded volume reduction in the atrium was induced by changing the elevation of the outflow catheter tip. Pressure reduction from 6 cm H2O atrial distension resulted in a decrease in atrial distension volume. Atrial distension by 6cmH2O did not change the release of immunoreactive atrial natriuretic peptide (irANP). The graded reduction in atrial distension from 0.11 ± 0.03 (1.5 cm H2O) to 1.36 ± 0.19µl/mg wet weight (6.0cm H2O) resulted in 1.7 (6.76 ± 2.05 versus 3.83 ± 1.18pg/mg per min, n=9, P< 0.025) to 40.1-fold (77.66 ±17.82 versus 3.0 ± 1.14pg/mg per min, n=11, P<0.025) increases in irANP relese.IrANP release in response to the reduction of atrial distension was volume dependent. The relation of percentage increase in irANP release with the percentage reduction of a trial distension was exponential. The data suggest that the atrial muscle shortening, but not stretch per se, may be a potent direct stimulus for the regulation of irANP secretion.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Venous plasma noradrenaline (PNA) was recorded during a multistage exercise test in order to assess the possible role of excess sympathetic nervous system activity in young men at increased risk of developing essential hypertension, and to analyse whether any such involvement was associated with heredity and/or borderline hypertension. Four groups were evaluated: 28 normotensive (NTO) and 20 borderline hypertensive (BHO) offspring of hypertensives, 12 borderline hypertensives with normotensive parents (BH) and 28 normotensives with normotensive parents (NT). Analysis of variance showed that heredity per se was associated with an increased PNA response to light exercise. In NT, PNA correlated with age at rest and light exercise (r= 0.39-0.58, P<0.05-0.005). When the influence of age was controlled for by dividing the subjects into two age groups a more pronounced increase in PNA response to light exercise was found in the youngest age group of offspring hypertensives (17-26 years), whereas no differences between the groups were observed in the upper age group (27-40 years). Our results indicate the presence of a hyperreactivity of the sympathetic nervous system during light exercise in young offspring of hypertensives.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

This study investigated the effect of chronic intracerebroventricular (IVT) infusion of a hypertonic NaCI (400mmol/l) artificial cerebrospinal fluid (aCSF) on blood pressure and whole body pressor responsiveness, in control rats (CH) and in rats'implanted with deoxycorticosterone acetate (DOCA; DH). An isotonic aCSF was infused into another group of control (Cl) and DOCA (Dl) rats. Indirect systolic blood pressure (SBP) was measured using a tail-cuff technique once a week prior to and during the infusion period. Following 2 weeks of infusion, SBP increased significantly only in the DH and CH groups. In urethaneanaesthetized rats, the pressor response to intravenous infusions of norepinephrine and angiotensin II (Angll) increased significantly in DH rats. When compared with Cl and Dl rats, those from the CH group also exhibited an enhanced response to norepinephrine and Angll. However, this increase was not as great as in the DH animal. These results show that whole body pressor responses to norepinephrine and Ang II, increase in rats receiving chronic IVT infusion of hypertonic NaCI. These responses coincide with moderate but significant increases in SBP. These data indicate that sodium chloride acts at a central site to increase norepinephrine and Ang II pressor responsiveness in mineralocorticoid hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The development of blood pressure was monitored by the tail-cuff method in normotensive (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP) receiving ethanol (alcohol) in drinking water from weaning (approximately 1 month of age). Alcohol administration over a 3-month period attenuated the development of hypertension in SHRSP and also caused a small reduction of the initial blood pressure rise in WKY. This was accompanied by a reduction of fluid intake and an increase of circulating antidiuretic hormone (arginine vasopressin; AVP). Circulatory volume remained constant. Direct measurement of arterial blood pressure in conscious rats before and after autonomic blockade confirmed the antihypertensive effect of alcohol in SHRSP and indicated that it is at least partly dependent on altered activity of neural mechanisms. Sudden withdrawal of alcohol caused an immediate increase of fluid intake followed by a rise of blood pressure lasting several days in both WKY and SHRSP. This withdrawal hypertension could not be attributed to changes in plasma catecholamines or AVP.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Trypsin cleaved plasma angiotensinogen with apparent first-order kinetics and generated an angiotensin I (Ang I) immunoreactive material. Size exclusion high-performance liquid chromatography (HPLC) of rat plasma proteins demonstrated that the Ang I immunoreactive material was formed in those fractions which contained angiotensinogen. The Ang I immunoreactive material was higher in nephrectomized rat plasma than normal plasma, in accordance with the higher angiotensinogen concentration. These findings indicated that angiotensinogen could be the source of the Ang I immunoreactive material. Purification of the Ang I immunoreactive material by cation-exchange chromatography followed by reverse-phase HPLC demonstrated an elution pattern close to that of human tetradecapeptide. The purified Ang I immunoreactive material was cleaved by pure mouse submandibular renin to Ang I, exclusively. Incubation at 37°C of the Ang I immunoreactive material with plasma partially destroyed the angiotensin immunoreactive material. These findings demonstrated that the angiotensin immunoreactive material was an Ang I containing tetradecapeptide (TDP)-like peptide, unstable during a renin incubation step, leading to erroneous values for plasma inactive renin if not removed. The Ang I immunoreactive material was removed by cation-exchange chromatography of trypsin-activated plasma allowing for a determination of inactive renin. The presence of inactive renin in plasma from normal and nephrectomized rats was confirmed, and identified by neutralization and immunoprecipitation with antirenins. These findings should enable us to develop a routine assay for plasma inactive renin in rat plasma.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The effect of cromakalim, a K+-channei activator, on the intracellular concentration and transmembrane fluxes of Na+and K+, was studied in 18 normal male subjects, using a double-blind parallel study design. After a run-in period on placebo for 1 week the subjects were treated with either placebo (n=6) or cromakalim (n=12) for 1 week. Blood pressure was not changed during cromakalim administration in these normal male subjects but heart rate was increased. The intraerythrocyte and intraleucocyte K+concentration was decreased during cromakalim administration while the Ca2+-dependent K+channels in the red blood cells were increased. No significant effect of cromakalim could be demonstrated on the intracellular Na+and Mg2+concentration, on the ouabain-sensitive or bumetanide-sensitive 86Rb uptake and on the maximal3H-ouabain binding in erythrocytes and leucocytes. The red cell Na+Li+countertransport, anion carrier and ground membrane leak of Na+and K+were also not changed in the cromakalim-treated subjects.

ISSN:0263-6352    

出版商:OVID    

年代:1989

数据来源: OVID