摘要:

BackgroundPlatelet derived growth factor (PDGF)-BB is an important vascular smooth muscle cell (VSMC) mitogen. PDGF-BB induces an increase in intracellular free calcium concentration ([Ca2+]i), an activation of mitogen-activated protein (MAP) kinase and an increase in DNA synthesis. The increase in [Ca2+]iis thought to be an important second messenger in the intracellular signalling cascade, leading to growth of VSMC.ObjectiveThe aim of the present study was to elucidate the role of the PDGF-BB-induced increase in [Ca2+]iin the activation of MAP kinase and increase in DNA synthesis. Binding of [Ca2+]iwas performed by the intracellular chelator bis-(2-amino-5-methylphenoxy) ethane-N,N,N′,N′-tetraacetic acid tetraacetoxymethyl ester (MAPTAM).MethodsCa2+levels were measured by the Fura-2 method. MAP kinase activation was determined by Western blotting. DNA synthesis was determined by measurement of incorporation of [3H]-thymidine into the cell DNA.ResultsAdministration of 50 ng/ml PDGF-BB induced an increase in [Ca2+]i, an activation of MAP kinase and an increase in DNA synthesis. In bis-(2-amino-5-methylphenoxy) ethane-N,N,N′,N′-tetraacetic acid tetraacetoxymethyl ester (MAPTAM)-treated cells the PDGF-BB-induced effect on [Ca2+]iwas totally blunted, whereas no effect on MAP kinase activation and DNA synthesis could be observed.ConclusionsThese findings show that the effect of PDGF-BB on MAP kinase activation is independent of calcium level. [Ca2+]i might be implicated in the PDGF-BB-induced mitogenic process only in conjugation with other signalling components.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveOur study was designed to investigate whether angiotensin II subtype 1 (AT1) receptors are involved in the constrictor responses evoked by endothelin-1 and the thromboxane A2analogue U46619 in aortic rings from spontaneously hypertensive rats (SHR), by studying the effect of the AT1receptor antagonist losartan. In addition, since nitric oxide seems to participate in the mechanism of action of losartan, we studied the effect of the nitric oxide synthesis inhibitor,NG-nitro-L-arginine methyl ester (L-NAME), on the action of losartan.Materials and methodsDose-response curves of either endothelin-1 (10−10to 10−7mol/l) or U46619 (10−10to 10−6mol/l) were studied in the presence or absence of losartan (10-5mol/l) in aortic rings from SHR. Likewise, similar experiments were done in aortic rings pretreated with the nitric oxide synthesis inhibitor, L-NAME (10−4mol/l).ResultsPre-incubation with losartan significantly reduced the contractile response to endothelin-1 compared with control rings, without modifying the value represented by 50% of the maximal response (pD2). The concentration-response curve to U46619 was shifted to the right in the presence of losartan, reducing the pD2compared with control rings. The presence of captopril (10-5mol/l) in the incubation media did not alter the response to either endothelin-1 or U46619. The diminished response to both endothelin-1 and U46619 in the presence of losartan was reversed in L-NAME-pretreated rings.ConclusionsAngiotensin II seems to participate in the vasoconstriction induced by both endothelin-1 and the thromboxane A2analogue through the stimulation of AT1receptors in SHR aortic rings, because losartan inhibited this effect. Moreover, nitric oxide appears to be involved in this action of losartan.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundCellular aspects of remodelling have not been investigated fully in intact vessels due to lack of appropriate methodology.ObjectiveTo determine the cellular alterations induced by chronic inhibition of nitric oxide (NO) production in intact rat basilar arteries by combined use of perfusion myography and a laser scanning confocal microscope.MethodsWistar–Kyoto rats were treated with 10 mg/kg per day NG-nitro-L-arginine methyl ester (L-NAME) for 3 weeks. Basilar arteries from treated and age-matched Wistar–Kyoto rat controls were mounted on a perfusion myograph, stained with the nuclear dye Hoechst 33 342 and fixed under pressure. The segments were mounted on a slide and visualized using the 364 nm line of a laser scanning confocal microscope. MetaMorph software was used to obtain optical sections from the vessel and for morphology determinations.ResultsL-NAME treatment induced hypertension (systolic blood pressure control 129.2 ± 2.7 mmHg and SBP L-NAME treatment 176.3 ± 5.2 mmHg,P< 0.001). Compared with control rat arteries, arteries from treated rats had a reduced lumen diameter, similar wall thickness and an increased wall: lumen ratio. L-NAME treatment induced specific changes in adventitia, media and intima, namely an increase in number of adventitial cells and in adventitia thickness, a reduction in number of smooth muscle cells with no change in media thickness and reductions in number of endothelial cells, size of nuclei and luminal surface area.ConclusionsHypertension induced by chronic inhibition of NO production is associated with eutrophic remodelling of rat basilar artery. However, within this overall maintenance of constant volume, there are marked cellular changes in adventitia, media and intima. The separate contributions of inhibition of NO production and hypertension to the remodelling process need to be elucidated.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveHuman and rat adipose tissue contain very high levels of natriuretic peptides clearance receptor messenger (m)RNA, and fasting inhibits its gene expression in adipose tissue. In this study we evaluated plasma atrial natriuretic peptide (ANP) and gene expression of biologically active type A natriuretic peptide receptor (NPr-A) and clearance natriuretic peptide receptor (NPr-C) in adipose tissue of obese hypertensive and obese normotensive patients.Design and methodsWe studied 27 untreated obese hypertensives, 26 obese normotensives (body mass index ≥ 30 kg/m2), 24 non-obese essential hypertensives and 23 lean healthy subjects (body mass index ≥ 25 kg/m2). Blood samples were withdrawn for ANP, plasma renin activity and aldosterone radio-immunoassays. Subcutaneous peri-umbilical adipose tissue samples were obtained, by needle aspiration, in 13 obese hypertensives and in 12 obese normotensives and used for RNA extraction. Then, complementary synthesis and semiquantitative polymerase chain reaction (PCR) with primers complementary to sequences of different exons of the genes encoding for NPr-A, NPr-C and β-actin, were performed.32P-labeled PCR products were separated by electrophoresis, blotted onto nylon membranes, and the exposed autoradiographic films were analysed by densitometry. NPr signals were normalized by the β-actin expression level.ResultsPlasma ANP was lower in obese hypertensives than in obese normotensives (37.5 ± 7 versus 43.2 ± 6 pg/ml,P< 0.05), but was higher in non-obese hypertensives than in non-obese normotensives. In contrast, plasma renin activity and aldosterone were higher in the obese hypertensives. Although NPr-A and NPr-C expression were not statistically different between the two obese groups, the NPr-A: NPr-C mRNA ratios were significantly lower in obese hypertensives (P< 0.03).ConclusionsOur data suggest that in obese hypertensives compared to obese normotensives, the lower NPr-A: NPr-C ratio might determine decreased biological activity and/or an increased clearance of natriuretic peptide in adipose tissue, suggesting that the natriuretic peptide and its receptor system may be important in obesity-related hypertension where ANP levels are lower.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo evaluate the role of kinins in the hypotensive response to angiotensin converting enzyme inhibition, we compared the blood pressure effects induced by acute or chronic captopril administration in a mouse strain (Bk2r−/−) with disruption of the bradykinin B2receptor gene and in wild-type controls (J129 Sv mice). A second aim was to determine whether Icatibant, a selective bradykinin B2-receptor antagonist, prevented the blood pressure changes induced by acute captopril administration in Swiss, c57/B16, J129 Sv and Bk2r-/-mice.Methods and resultsUnder basal conditions, tail-cuff systolic blood pressure (SBP) and intra-arterial mean blood pressure (MBP) were higher in Bk2r-/-than in J129 Sv (SBP: 132 ± 2 versus 113 ± 3 mmHg; MBP: 144 ± 6 versus 122 ± 10 mmHg,P< 0.05 for both comparisons). Acute captopril administration (1 mg/kg body weight, intra-arterially) reduced the MBP of Bk2r-/-and J129 Sv by 36 ± 8 and 31 ± 7 mmHg, respectively. Swiss and c57/B16 mice showed similar decreases in MBP following captopril. Pretreatment with Icatibant (10 nmol/kg body weight, intra-arterially) did not influence the MBP responses to acute captopril in all the strains. Chronic administration of captopril (approximately 120 mg/kg body weight per day for 2 weeks in drinking water) reduced SBP in either Bk2r-/-or J129 Sv. The magnitude of this response was higher in Bk2r-/-than in J129 Sv (65 ± 3 versus 47 ± 4 mmHg, respectively,P< 0.01).ConclusionsOur results suggest that endogenous kinins do not participate in the hypotensive response to angiotensin converting enzyme inhibition in mice; in Bk2r-/-, the exaggerated blood pressure response to chronic captopril appears to be attributable to interference with unbalanced vasoconstrictor action of the renin–angiotensin system.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundPrevious studies have shown that molecular variants of the cytoskeletal protein adducin may be involved in regulation of blood pressure both in genetic rat hypertension and in human essential hypertension.ObjectiveTo investigate the relationship of genetic polymorphism of α-adducin with blood pressure, cardiovascular structure, and some biochemical indexes of cardiovascular risk in a sample of general population.Design and methodsA sample of 246 subjects (124 men and 122 women, aged 57.7 ± 3.7 years) was randomly chosen from a middle-aged population. Twenty-four-hour ambulatory blood pressure, as well as left ventricular mass (by echocardiographic methods) and carotid wall thickness (by B-mode ultrasound methods) were measured. DNA was extracted from peripheral blood samples; the Gly460Trp diallelic variant of human α-adducin was genotyped by polymerase chain reaction amplification and then allele-specific oligo hybridization.ResultsA trend toward higher 24 h ambulatory blood pressure values in subjects not treated with antihypertensive drugs was observed among carriers of Trp460 allele, although the differences did not attain statistical significance (at closest,P= 0.066 for a dominant effect of Trp460 on systolic blood pressure). When blood pressure was considered a dichotomous variable, allowing the inclusion of treated hypertensives), a higher prevalence of Trp460 allele among hypertensives was observed (0.188 versus 0.106 among normotensives,P= 0.02). There was no evidence of association either of left ventricular mass or of common carotid wall thickness with Gly460Trp polymorphism.ConclusionsIn this sample of a general population, the relationship of a genetic polymorphism of α-adducin with blood pressure values was rather weak. However, a population-based case–control analysis indicated that there was an association between Trp460 allele and hypertension, with a relative risk for subjects carrying at least one Trp460 allele of approximately 1.6. Further investigation of larger and different population samples in order to assess the role of adducin gene polymorphism as a marker of genetic predisposition to the development of hypertension is warranted.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveWe have reported that bradykinin (BK) excretion is increased in severely diabetic rats, independent of the activity of the main renal kininforming enzyme, true kallikrein (KLK). To further investigate the relationship between renal BK excretion and renal KLK in diabetes we studied the regulation of the renal kallikrein-like gene, rat kallikrein 7 (rKLK7), as well as of the KLK encoding gene, rKLK1, in streptozotocin-induced (STZ) diabetic rats.MethodsExperiments were performed in STZ-induced diabetic male Wistar rats and their non-diabetic controls (n = 7 each group). Twelve weeks after STZ injection, urinary KLK activity, glomerular filtration rate and total protein excretion were determined. After extraction of total renal cortical RNA, specific oligonucleotides were used to generate a reverse transcription–polymerase chain reaction (RT–PCR) products of renal cortical rKLK1 and rKLK7 messenger (m)RNA. Southern blot analysis of these RT-PCR products were hybridized with appropriate gene-specific oligonucleotide probes.ResultsAfter 12 weeks, the rats showed hyperglycemia, proteinuria and a reduced glomerular filtration rate. Renal kininogenase was reduced, as indicated by a reduction in the expression of rKLK1, as well as of the KLK-related gene, rKLK7.ConclusionsOur data show that the expression of the two principal renal KLK genes is downregulated in the renal cortex of STZ-diabetic rats. We suggest that under severe diabetic conditions the rise in urinary BK excretion is not related to activation of the renal kinin-forming enzyme system.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo search for alterations of cytosolic pH and cell calcium handling in platelets and erythrocytes of Dahl rats susceptible and resistant to salt-induced hypertension.Design and methodsBlood pressure, plasma lipids, platelet cytosolic calcium concentration ([Ca2+]i) and pH (pHi) together with thrombin-induced changes in these parameters as well as erythrocyte [Ca2+]iand45Ca influx were determined in Dahl salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) rats aged 9, 15 and 24 weeks, which were fed a low-salt diet (0.3% NaCl), and in animals fed high-salt diet (4% NaCl) for 5–10 weeks since weaning.ResultsWith a low salt intake platelet pHiwas lower in SS/Jr than it was in SR/Jr rats, whereas basal platelet [Ca2+]iwas similar in rats of both strains. The difference in basal pHibetween SS/Jr and SR/Jr rats increased progressively with age of animals. A high salt intake from youth did not influence platelet [Ca2+]iin rats of either strain but it caused an earlier decrease in pHiin SR/Jr than it did in SS/Jr rats. Thrombin stimulation induced similar elevations of pHiand [Ca2+]iin rats of both strains, irrespective of age, salt intake and response of blood pressure to salt intake. Erythrocyte45Ca influx and [Ca2+]iwere greater for SS/Jr rats but only the latter parameter was correlated positively to blood pressure. Both regulation of platelet pHiand erythrocyte Ca2+handling were significantly related to plasma lipid levels.ConclusionsPlatelets of SS/Jr rats fed a low-salt diet were characterized by a lower basal cytosolic pHibut unchanged [Ca2+]irelative to those of SR/Jr rats. Hypertension induced by high salt intake was associated with increased erythrocyte [Ca2+]ibut not with elevation of platelet [Ca2+]ior alteration of response to stimulation with thrombin.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundPrevious studies have shown that farnesol, a 15-carbon nonsterol derivative of mevalonic acid, inhibits vasoconstriction. Because of its lipophilic properties, we hypothesized that farnesol increased membrane dynamics, thus reducing uptake of Ca2+and contraction.ObjectiveTo characterize the effect of farnesol on cell membrane fluidity.DesignThe study was conducted using A7r5 cells, a rat aortic vascular smooth muscle cell line. Inhibition of Ca2+uptake by farnesol was first established in these cells. Then, the effect of farnesol on membrane dynamics was determined. Finally, to ascertain that activation of Ca2+extrusion and reuptake processes by farnesol did not occur, Ca2+-ATPase activity was examined.MethodsMembrane fluidity in cell homogenates was estimated using two fluorescent dyes (1,6-diphenyl-1,3,5-hexatriene) and (1-[-(trimethylamino)-phenyl]-6-phenyl-1,3,5-hexatriene). Ca2+uptake was determined by monitoring the changes in cytosolic Ca2+concentration ([Ca2+]i) in fura-2-loaded cells after addition of KCl. Ca2+-ATPase activity was measured in 100 000 ×gcell fractions.ResultsFarnesol reduced KCl-induced [Ca2+]itransients significantly (P< 0.001), but did not modify membrane dynamic properties [0.214 ± 0.007 versus 0.218 ± 0.007 (n = 10) and 0.142 ± 0.002 versus 0.146 ± 0.003 (n = 5) for 1-[-(trimethylamino)-phenyl]-6-phenyl-1,3,5-hexatriene and 1,6-diphenyl-1,3,5-hexatriene anisotropies, respectively; NS]. Administration of up to 30 μmol/l farnesol did not affect Ca2+-ATPase activity.ConclusionFarnesol inhibits KCl-dependent rise of [Ca2+]iin A7r5 cells. This effect of farnesol is not related to a global change in plasma membrane lipid organization or to activation of Ca2+pumps. Other mechanisms such as direct inhibition of voltage-dependent Ca2+channels could therefore explain the biologic action of farnesol in the vascular tissue.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundIn familial hyperaldosteronism type I (FH-I), glucocorticoid treatment suppresses adrenocorticotrophic hormone-regulated hybrid gene expression and corrects hyperaldosteronism.ObjectiveTo determine whether the wild-type aldosterone synthase genes, thereby released from chronic suppression, are capable of functioning normally.MethodsWe compared mid-morning levels of plasma potassium, plasma aldosterone, plasma renin activity (PRA) and aldosterone: PRA ratios, measured with patients in an upright position, and responsiveness of aldosterone levels to infusion of angiotensin II (AII), for 11 patients with FH-I before and during long-term (0.8–14.3 years) treatment with 0.25–0.75 mg/day dexamethasone or 2.5–10 mg/day prednisolone.ResultsDuring glucocorticoid treatment, hypertension was corrected in all. Potassium levels, which had been low (< 3.5 mmol/l) in two patients before treatment, were normal in all during treatment (mean 4.0 ± 0.1 mmol/l, range 3.5–4.6). Aldosterone levels during treatment [13.2 ± 2.1 ng/100 ml (mean ± SEM)] were lower than those before treatment (20.1 ± 2.5 ng/100 ml,P< 0.05). PRA levels, which had been suppressed before treatment (0.5 ± 0.2 ng/ml per h), were unsuppressed during treatment (5.1 ± 1.5 ng/ml per h,P< 0.01) and elevated (> 4 ng/ml per h) in six patients. Aldosterone: PRA ratios, which had been elevated (> 30) before treatment (101.1 ± 25.9), were much lower during treatment (4.1 ± 1.0,P< 0.005) and below normal (< 5) in eight patients. Surprisingly, aldosterone level, which had not been responsive (< 50% rise) to infusion of AII for all 11 patients before treatment, remained unresponsive for 10 during treatment.ConclusionsApparently regardless of duration of glucocorticoid treatment in FH-I, aldosterone level remains poorly responsive to AII, with a higher than normal PRA and a low aldosterone: PRA ratio. This is consistent with there being a persistent defect in functioning of wild-type aldosterone synthase gene.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID