ISSN:1018-1172    

DOI:10.1159/000159068

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The glycocalyx of the endothelium of the systemic arteries and vena cava of the rabbit was visualised by in situ perfusion fixation with glutaraldehyde containing Alcian blue. The thickness of the layer ranged from 45 ± 1 nm in the coronary artery to 81 ± 2 nm in the carotid. The glycocalyx was 20 ± 1.5 nm thicker on the downstream side of intercostal ostia than on the upstream side. Changes in the staining pattern with increasing concentrations of MgCl2 indicated that carboxyl groups made the major contribution to the surface charge, though sulphate groups were also present, particularly in the aortic arch and carotid artery. Segments of the thoracic aorta and carotid artery were also stained in vitro with fluorescence labelled wheat germ agglutinin, and fluorescence intensity in histological sections was quantified using a video microscope equipped with a microcomputer-based image analysis system. The fluorescence intensity in the carotid was 1.65 ± 0.15 times that in the aorta. Pretreatment with neuraminidase reduced fluorescence intensity by 60 ± 4% in the carotid and 53 ± 2% on the upstream side of intercostal ostia, but only by 37 ± 3% on the downstream side. Chondroitinase and heparanase both reduced binding and when used together their effect was additive, reducing fluorescence by 27 ± 3, 51 ± 4, and 32 ± 3% at the three sites, respectively. Though the interpretation of the lectin binding experiments is complicated by a number of factors, these results support previous reports that sialyl groups are abundant in the endothelial glycocalyx. Glycosaminoglycans are also present, however, in significan

ISSN:1018-1172    

DOI:10.1159/000159025

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

It is well recognized that following binding of ligand, many receptors undergo a process of agonist-induced receptor-mediated endocytosis (RME) or internalization. We recently characterized the intracellular pathway and kinetics of angiotensin II (AII)-RME in cultured explant-derived rat aortic vascular smooth muscle cells (VSMCs). To definitively study vascular internalization of AH, however, it is critical to examine AII binding and uptake in intact, differentiated VSM. For the present study, we used a unique, biologically active All-colloidal gold conjugate to qualitatively examine, by transmission electron microscopy, the ultrastructural details of AII binding and internalization in intact VSM. Strips of isolated, cleaned, and denuded rat aortic smooth muscle were incubated with All-gold probe for 2 h at 4° C to allow binding of the complex without simultaneous internalization. After rinsing to remove unbound All-gold, the strips were incubated at 37 °C (5–90 min) to initiate internalization. These studies show that AII initially binds over the entire surface of medial VSMCs. Following binding the AII is internalized via small receptosomes which likely represent clathrin-coated vesicles. By 20 min after internalization, gold particles are evident within large lysosome-like vesicles deep within the VSM. There was no evidence of association of gold particles with the Golgi network at any of the time periods examined. Gold particles were occasionally observed in perinuclear regions after 90 min at 37°C, although this did not appear to represent a typical pattern. AII-gold binding and internalization were selective: control probe (no AII) did not internalize; Losartan potassium (selective AT1 receptor antagonist) effectively competed for All-gold binding and internaliza

ISSN:1018-1172    

DOI:10.1159/000159026

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000317452

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

In rings of rat aorta, cyclopiazonic acid (CPA), a selective inhibitor of the internal membrane Ca2+-pump ATPase, gradually initiated a concentration-dependent contraction which was much less in endothelium-intact than in endothelium-denuded rings. In phenylephrine-precontracted rings with intact endothelium, CPA, like acetylcholine, produced endothelium-dependent relaxations in a concentration-dependent manner. These were nearly abolished by methylene blue (MB) or NG-nitro-L-arginine methylester (L·NAME). This inhibitory effect of L·NAME was reversed by L·arginine but not by D-arginine, indicating that CPA induced a release of endothelium-derived relaxing factor (EDRF) from endothelial cells leading to smooth muscle relaxation. Concentration-dependent relaxations induced by sodium nitroprusside, which is thought to act by releasing nitric oxide, were not inhibited by L·NAME, but were inhibited similarly by MB in endothelium-intact and -denuded rings. These results indicate that CPA causes EDRF-release from endothelial cells and support the recent hypothesis that release of intracellular Ca from stores is the initiating factor in EDRF release, possibly allowing ongoing Ca entry to sustain rele

ISSN:1018-1172    

DOI:10.1159/000159027

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The effect of 12-14 weeks streptozotocin-induced diabetes on contractile responses of the highly innervated caudal artery to adrenergic nerve stimulation was studied. The maximum contractile response and sensitivity (as reflected by the pD2 value) to noradrenaline (NA) was significantly greater in diabetic than in control caudal arteries. The maximum contractile response, but not sensitivity, to tyramine was significantly enhanced in diabetic compared with control caudal arteries when expressed as stress (mN/mm2), but not when expressed as a percentage of the maximum NA response obtained previously in the same tissues. No significant difference was detected between the responses of control and diabetic caudal arteries to electrical field stimulation of adrenergic nerves, when expressed either as stress or as a percentage of the corresponding NA response. Pretreatment with phentolamine markedly inhibited the contractile responses to field stimulation of both diabetic and control caudal arteries, while 6-hydroxydopamine essentially abolished responses to electrical field stimulation and tyramine in both tissues. Finally, pretreatment with hydrocortisone, timolol, and desipramine increased sensitivity to NA in control and diabetic caudal arteries by a similar magnitude. Thus, the enhanced contractile responses of caudal arteries from diabetic rats to NA do not appear to be associated with the development of autonomic neuropathy.

ISSN:1018-1172    

DOI:10.1159/000159028

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000317453

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Allylamine is an aliphatic amine that causes vascular lesions in aorta and medium-sized arteries. This primary amine has been shown to be metabolized to acrolein both in vivo and in vitro. Acrolein may cause allylamine’s toxic effects, since it acts as a strong peroxidizing agent itself; in addition, deamination of allylamine is accompanied by production of hydrogen peroxide. To investigate the relative roles of oxidative stress and lipid peroxidation in allylamine intoxication, we conducted an acute in vivo time-course study following administration of allylamine (150 mg/kg) to rats by gavage. Animals were sacrificed at 1, 3 and 5 h after allylamine treatment, and subcellular fractions of aorta, epicardium and endocardium were assayed for enzymes of the oxidant defense system and thiol (-SH) status, capacity for lipid peroxidation, and ‘OH radical generation. Results suggest that in vivo treatment with allylamine causes preferential damage to aortic mitochondria. A marked depletion of total and free -SH content was found in aorta, epicardium and endocardium, with a striking increase in the formation of thiobarbiturate-reactive substance by aortic mitochondria at all time points. A significant increase in the capacity to generate ‘OH was found in aorta (with lesser increases in epicardium and endocardium) after allylamine treatment. Levels of defense system enzymes were not consistently altered, however. In a totally in vitro experiment, liposomes incubated with acrolein (0.2–2 mM) showed a proportional increase in lipid peroxidation of liposomal membrane. A likely basis of allylamine’s cardiovascular toxicity is acrolein-induced lipid peroxidation, especially in mit

ISSN:1018-1172    

DOI:10.1159/000159029

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Endothelial cell contraction plays a pivotal role in the increased extravasation of fluid and macromolecules in vascular leakage. Previous studies have indicated that elevation of the adenosine 3’,5’-cyclic monophosphate (cAMP) concentration can improve the endothelial barrier function. In analogy with smooth muscle cell contraction, which is inhibited by both cAMP and guanosine 3’,5’-cyclic monophosphate (cGMP), we have compared the role of cAMP and cGMP in the regulation of the permeability of human endothelial cell monolayers. The cellular cGMP concentration was elevated 3- to 5-fold after addition of 10–7M atrial natriuretic peptide (ANP) or 10-4M sodium nitroprusside (SNP), both under basal and thrombin-stimulated conditions. After exposure to thrombin, cGMP generation by ANP or SNP or addition of 8-bromo-cGMP significantly suppressed the increase in permeability. Inhibition of nitric oxide production with 10–4 M NG-nitro-L-arginine methyl ester increased the permeability of endothelial monolayers in the majority of the tested cultures, an effect that could be counteracted by addition of 8-bromo-cGMP or ANP. An increase of cAMP upon the addition of forskolin reduced the permeability in all endothelial cell strains under basal conditions and after exposure to thrombin. The forskolin- and 8-bromo-cGMP-mediated decreases in permeability were accompanied by increases in transendothehal electrical resistance. These in vitro data indicate that, in addition to cAMP, cGMP can act as a potent fine-regulator of endothelial p

ISSN:1018-1172    

DOI:10.1159/000159030

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000317454

出版商:S. Karger AG    

年代:1994

数据来源: Karger