ISSN:1062-3329    

DOI:10.3109/10623329309102687

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Endothelial cells synthesise nitric oxide from L-arginine and this process can be inhibited by NG, NGdimethylarginine (asymmetric dimethylarginine; ADMA), a constituent of plasma and urine. In the present study cultures of human umbilical vein endothelial cells have been shown to release ADMA. Over 7 days 5.1±2.8;μg ADMA was produced by 107cells (n = 8). These results suggest the presence of a metabolic pathway that may regulate NO synthesis within the endothelium.

ISSN:1062-3329    

DOI:10.3109/10623329309102688

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

The interactions between L-arginine, the source of nitric oxide formation, and NG-nitro-L-arginine (L-NOARG), an inhibitor of nitric oxide synthase were examined in isolated rat aorta. Carbachol induced endothelium-dependent relaxation was used to study the constitutive form of the enzyme, whereas the loss of contraction tonicity to phenylephrine following incubation of endothelium free rings with interleukin 1 was used to investigate the smooth muscle inducible form. L-NOARG is a potent inhibitor of the two types of the enzyme in the rat aorta. However, the effects of L-NOARG on the constitutive (endothelial) vascular NO synthase were partially prevented, but not reversed, by L-arginine. In contrast, L-arginine fully reversed the action of L-NOARG on the smooth muscle inducible form of NO synthase. The selective reversibility of L-NOARG on the inducible, by comparison with the constitutive form of nitric oxide synthase present in the vasculature, may represent a limitation in the use of this type of compounds in the treatment of the systemic arterial hypotension observed during septic shock.

ISSN:1062-3329    

DOI:10.3109/10623329309102689

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Purified particulate endothelial nitric oxide (NO) synthase requires NADPH, Ca2+, calmodulin, and 5,6,7,8-tetrahydrobiopterin (BH4) for enzymatic conversion of l-arginine to l-citrulline and NO. We now report that the purified particulate endothelial enzyme has both FAD and flavin mononucleotide bound to the enzyme in equimolar amounts and this amount of bound flavin is sufficient for full activity of the enzyme. Also, we found that over 90% of the biopterin bound to the enzyme is in the reduced form of 5,6,7,8-tetrahydrobiopterin. However, the small amount of bound biopterin is not sufficient for maximal activity.

ISSN:1062-3329    

DOI:10.3109/10623329309102690

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

The importance of glycosylation to endothelin (ET) receptors was studied in cultured Swiss 3T3 fibroblasts. ET stimulated phosphatidylinositol hydrolysis by 270% in control cells. This stimulatory effect was decreased to<130% in tunicamycin (TU)-treated cells. TU inhibited protein glycosylation, but did not effect DNA synthesis, cell morphology, or cell numbers. ET-1 binding was greatly reduced in TU-treated cells. In membranes prepared from control cells, [125]ET-1 binding was saturable, and appeared as a straight line in Scatchard analysis with values of 0.7 pmol/mg and 0.9 nM for Bmaxand KD, respectively. [125]ET-1 binding to membranes from TU-treated cells was not saturable. Scatchard analysis showed a biphasic line. Values of Bmax, and KDfor the higher affinity site were 0.17 pmol/mg and 0.12 nM, respectively. The low affinity site exhibited a much weaker affinity for ET with an estimated KDvalue of 6.8 nM. Cross-linking studies revealed that the receptor in control membranes was a protein with a molecular mass of 62 kDa. In membranes from TU-treated cells, two proteins with molecular masses of 62 and 40 kDa were labeled. These data suggest that receptor glycosylation was required for ET binding and the subsequent activation of the phosphatidylinositol hydrolysis pathway.

ISSN:1062-3329    

DOI:10.3109/10623329309102691

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Using a differential screening strategy, clone 133 was identified as an immediate early gene induced by interleukin-1 (IL-1) in human endothelial cells (HEC). The sequence of the cDNA revealed identity with a recently identified member of the inhibitors of nuclear factor kB family (IkB). IkB/clone 133 is expressed at low levels in unstimulated endothelial cells and is rapidly induced by the inflammatory cytokines IL-1 and tumor necrosis factorα(TNFα*), but not interleukin-6. Inducibility by IL-1 is abolished by the IL-1 receptor antagonist. Cycloheximide superinduces IkB/clone 133 expression in HEC. IL-1 and TNFαhave little or no effect on IkB/clone 133 expression in a fibrosarcoma cell line responsive to these polypeptide mediators. These results show for the first time cytokine-inducible lineage-specific expression of a member of the IkB family.

ISSN:1062-3329    

DOI:10.3109/10623329309102692

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Development of the human placenta is characterized by continous angiogenesis which proceeds until term pregnancy which makes the placenta a unique model system for the studies of normal human angiogenesis. This report compares the patterns of PDGF-B and PDGFβ-receptor protein expression in microcapillaries to those of larger blood vessels. Endothelial cells of microcapillaries co-express PDGF-B and PDGFβ-receptor protein as analyzed by immunohistochemical staining of frozen sections of term placenta. Endothelial cells of larger vessels expressed the PDGF-B protein whereas PDGFβ-receptor protein was not detectable. Positive staining with receptor antibodies was detected in the surrounding pericytes and smooth muscle cells. These data support the hypothesis that capillary endothelial cells proliferate via a PDGF-mediated autocrine loop. Endothelial cells situated in larger vessels, on the other hand, may stimulate growth of the vessel intima by paracrine interactions.

ISSN:1062-3329    

DOI:10.3109/10623329309102693

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

In vitroexperiments were designed to investigate the effect of low oxygen tensions on tissue-type plasminogen activator (t-PA) production by vascular endothelium. Cultured human umbilical vein endothelial cells were submitted for 1–8 h to hypoxia (30 mm Hg). t-PA antigen, measured by specific enzyme-linked immunosorbent assay (ELISA), was found significantly decreased either in culture supernatants or in cell lysates/extracellular matrix. By contrast, the secretion of plasminogen activator inhibitor-1 (PAI-1), also measured by specific ELISA, was not affected. Addition of superoxide dismutase (a superoxide anion scavenger) or oxypurinol (a xanthine oxidase inhibitor) to monolayers before hypoxia prevented t-PA modification. The flavonoid rutin (a hydroxyl radical scavenger) also presented a protective effect whereas catalase (a hydrogen peroxide scavenger) was inefficient. These results suggest that hypoxia stimulates endothelial cells to produce oxygen radicals and in particular xanthine oxidase-derived superoxide anions which mediate the inhibition of t-PA production.

ISSN:1062-3329    

DOI:10.3109/10623329309102694

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Uremia, when treated with chronic dialysis, accelerates atherogenesis and its attendant complications. Using a chronic exposure modelin vitro, it has previously been shown that uremic concentrations of oxalic acid inhibit endothelial cell (EC) proliferation and migration. In this paper the permeability of ECs to oxalate and the effect of oxalate on the proliferation of ECs stimulated by heparin-binding growth factors are studied. ECs were permeable to [14C]oxalate with uptake dependent on external oxalate concentration and efflux dependent on temperature, time, and external oxalate concentration (allP<0.0001). The proliferation of unstimulated cultures and cultures stimulated with basic fibroblast growth factor (bFGF), endothelial cell growth supplement,αendothelial cell growth factor andβendothelial cell growth factor was inhibited by exposure to oxalate in all experiments from 14 to 100% in 14 to 60 d (N=19, allP<0.001). Furthermore, surviving cultures were converted from the proliferative to the quiescent state. The proliferation of neither fibroblasts nor BALB/c 3T3 cells was altered by oxalate. Oxalate modified neither the binding of [125I]bFGF to specific EC membrane receptors nor receptor density. Furthermore, oxalate did not interfere with the interaction of bFGF and its cofactor heparin. We conclude that uremic concentrations of oxalate inhibit the proliferation of ECs stimulated with heparin-binding growth factors.

ISSN:1062-3329    

DOI:10.3109/10623329309102695

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

In this study we examined the effect of 4,12 and 16 weeks of hypercholesterolemia, induced by feeding a 0.3% cholesterol enriched diet, on endothelial function in rabbit aorta. Endothelial function was assessed by measuring acetylcholine (ACh) induced endothelium dependent relaxations in isolated aorta and ACh induced release of Endothelium Derived Relaxing Factor (EDRF) from the endothelium. In all groups (4, 12 and 16 weeks) hypercholesterolemia was accompanied by a significant rise of total serum cholesterol and HDL-cholesterol/total cholesterol ratio. The intirnal surface of the total aorta covered by atherosclerotic fatty streaks after 4, 12 and 16 weeks of hypercholesterolemia was 33.8±3.3%, 44.1±5.2% and 55.6±6.1% respectively. After 4 weeks of hypercholesterolemia endothelium dependent relaxations to ACh were augmented while ACh induced EDRF release was not affected. In contrast 12 and 16 weeks of hypercholesterolemia significantly reduced both ACh induced EDRF release and endothelium dependent relaxations. Endothelium independent relaxations to sodium nitroprusside (SNP) were not affected by 4 and 12 weeks of cholesterol (0.3%) feeding but 16 weeks of hypercholesterolemia significantly enhanced vascular sensitivity to SNP. Plotting relative maximal endothelium dependent relaxations versus percent intimal lesions of donor segments or aortas revealed an inverse relationship between endothelial function and the extent of atherosclerosis. The results show that in diet induced experimental atherosclerosis, endothelial dysfunction is a time related process.

ISSN:1062-3329    

DOI:10.3109/10623329309102696

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor