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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied whether endothelin-1 (ET-1) would affect its own synthesis. Human umbilical cord vein endothelial cells in methionine-poor culture medium containing [35S] methionine were treated with synthetic ET-1 or ET-3. Immunoprecipitation of 35 S-labeled ET-1 was performed with rabbit ET-1 antiserum. ET-1 caused an 40 +/- 4% (mean +/- SEM) increase of immunoprecipitable 35 S-labeled ET-1 as confirmed by its elution point in reversed phase high power liquid chromatography (HPLC). ET-3 caused a 23 +/- 2% increase in ET-1 concentration. Amplification of cDNA by PCR showed both ET-1 and ETB receptor mRNAs in human cord vein endothelial cells. We conclude that ET-1 increases its own synthesis in endothelial cells. This suggests a positive autocrine feed-back action of ET-1 on its own synthesis, an effect which is probably mediated by non-specific ETB receptors.
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PMID:Endothelin-1 stimulates its own synthesis in human endothelial cells. 141 49

Our aim was to characterize and determine the function of endothelin (ET) receptor subtypes in human vascular tissue. Reverse transcriptase-polymerase chain reaction with nested oligonucleotide primers detected the presence of mRNA encoding both ETA and ETB receptors in the media from aorta and pulmonary and coronary arteries. In situ hybridization confirmed the presence of mRNA for both subtypes in the media of coronary arteries. Saturation binding assays using 125I-ET-1 found a single population of high-affinity ET receptors (n = three patients, +/- SEM) in aorta (Kd = 0.507 +/- 0.020 nM; Bmax = 9 +/- 4 fmol/mg protein) and pulmonary (Kd = 0.845 +/- 0.245 nM; Bmax = 15 +/- 10 fmol/mg protein) and coronary arteries (Kd = 0.141 +/- 0.020 nM; Bmax = 71 +/- 21 fmol/mg protein). Using media from coronary arteries, the ETA-selective ligand BQ123 (cyclo[D-Asp-L-Pro-D-Val-L-Leu-D-Trp]) and the ETB-selective ligand BQ3020 (Ala11,15-Ac-ET-1[6-21]) both produced biphasic competition binding curves against 125I-ET-1, confirming the presence of high- and low-affinity sites corresponding to the two subtypes: BQ123 (KdETA = 0.85 +/- 0.03 nM; KdETB = 7.58 +/- 2.27 microM; ETA/ETB, 87%:13%) and BQ3020 (KdETA = 0.22 +/- 0.04 microM; KdETB = 0.77 +/- 0.34 nM; ETA/ETB, 62%:38%). BQ123 (0.1 microM) caused a significant parallel rightward shift of ET-1-induced vasoconstriction of coronary arteries in vitro, but BQ3020 and Ala1,3,11,15-ET-1 failed to show any agonist activity when tested at concentrations of < or = 3 microM in three vessels.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Human endothelin receptors characterized using reverse transcriptase-polymerase chain reaction, in situ hybridization, and subtype-selective ligands BQ123 and BQ3020: evidence for expression of ETB receptors in human vascular smooth muscle. 750 50

To investigate the pathophysiologic role(s) of endothelin-1 (ET-1) in pulmonary hypertension, we studied the expression of ETB-receptor mRNA in the lung and venous plasma concentrations of ET-1 in rats with monocrotaline-induced pulmonary hypertension (PH). Three weeks after s.c. injection of monocrotaline (60 mg/kg), rats (PH rats, n = 6) were sacrificed. Vehicle-injected rats (n = 6) served as controls. The right ventricular systolic pressure of PH rats [58.0 +/- 4.7 mm Hg (mean +/- SEM)] was significantly higher than that in the vehicle-treated control rats (29.2 +/- 2.1; p < 0.01). Northern blot analysis showed that the expression of ETB-receptor mRNA decreased in the lung of PH rats. The venous plasma concentration of ET-1 measured by a sandwich-enzyme immunoassay was significantly higher in PH rats than in control rats (5.1 +/- 0.7 versus 1.3 +/- 0.2 pg/ml; p < 0.01). The present findings suggest that the expression of ETB-receptor mRNA decreases in the lung of PH rats, which might be closely related to the increase in plasma ET-1 concentration in these rats.
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PMID:Altered expression of ETB-receptor mRNA in the lung of rats with pulmonary hypertension. 750 80

Compelling evidence indicates that the endothelium-derived potent vasoconstrictor endothelin-1 (ET-1) stimulates aldosterone secretion by interacting with specific receptors. Although two different ET-1 receptors have been identified and cloned, the receptor subtype involved in mediating aldosterone secretion is still unknown. Accordingly, we wished to investigate whether the genes of ET-1 and of its receptors A and B are expressed in the normal human adrenal cortex. We designed specific primers for ET-1 and the ETA and ETB receptors genes and developed a reverse transcription polymerase chain reaction (RT-PCR) with chemiluminescent quantitation of the cDNA. In addition, we carried out 125I ET-1 displacement studies with cold ET-1, ET-3 and the specific ETA and ETB ligands BQ123 and sarafotoxin 6C. Localization of each receptor subtype was also investigated by autoradiography. Binding experiments were first individually analyzed by Scatchard and Hofstee plot and then coanalyzed by the nonlinear iterative curve fitting program Ligand. Histologically normal adrenal cortex tissue, obtained from kidney cancer patients (n = 7), and an aldosterone-producing adenoma (APA), which is histogenetically derived from the zona glomerulosa (ZG) cells, were studied. Results showed that the ET-1, ETA and ETB mRNA can be detected by RT-PCR in all adrenal cortices as well as in the APA. The best fitting of the 125I ET-1 displacement binding data was consistently provided by a two-site model both in the normal adrenal cortex (F = 22.1, P < 0.0001) and in the APA (F = 18.4, P < 0.0001). In the former the density (Bmax) of the ETA and ETB subtype was 2.6 +/- 0.5 pmol/mg protein (m +/- SEM) and 1.19 +/- 0.6, respectively. The dissociation constant (Kd) of ET-1, ET-3, S6C, and BQ-123 for each receptor subtype resulted to be within the range reported for human tissue for the ETA and ETB receptors. In the APA tissue the Bmax tended to be lower (1.33 and 0.8 pmol/mg protein, for the ETA and ETB, respectively) but the Kd were similar. Autoradiographic studies confirmed the presence of both receptor subtypes on the ZG as well as on APA cells. Thus, the genes of ET-1 and both its receptor subtypes ETA and ETB are actively transcribed in the human adrenal cortex. Furthermore, both receptor subtypes are translated into proteins in ZG and APA cells.
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PMID:Gene expression, localization, and characterization of endothelin A and B receptors in the human adrenal cortex. 808 64

Animal kidneys are exquisitely sensitive to the effects of endothelin (ET), but little is known of its binding characteristics, isoform prevalence, or receptor subtype distribution in human kidney. We investigated these parameters using high-performance liquid chromatography, radioimmunoassay (RIA), and the recently synthesized ETA and ETB receptor-selective peptide ligands BQ123 (cyclo[D-Asp-L-Pro-D-Val-L-Leu-D-Trp-]) and BQ3020 (Ala11,15-Ac-ET-1[6-21]). Fresh-frozen normal segments of kidneys excised for carcinoma were solid-phase-extracted using Amprep C2 columns, and parallel eluates were oxidized. All were subjected to RIA for ET and pro-ET-1, in triplicate. ET isoforms were characterized by RP-HPLC and subsequent RIA of eluates. Total amounts of immunoreactive ET were 6.9 +/- 3.8 and 4.5 +/- 1.6 pmol/g wet weight in medulla and cortex, respectively. Reverse-phase high performance liquid chromatography showed peaks of immunoreactivity with retention times identical to synthetic ET-1 and metsulphoxide ET-1. ET-2, ET-3, and pro-ET-1 were not detected. Saturation assays using 0.01-8.0 nM 125I-ET-1 or 125I-BQ3020, gave Kd values (mean +/- SEM) of 0.17 +/- 0.04 and 0.36 +/- 0.06 nM, respectively, with Bmax values of 57.7 +/- 15.4 and 30.0 +/- 5.0 fmol/mg protein, respectively. Hill coefficients were 0.86 +/- 0.03 and 0.77 +/- 0.04, but a two-site fit was not preferred. Receptor autoradiography has detected both subtypes, mainly present in medulla, with ETB predominating.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Human kidney: endothelin isoforms detected by HPLC with radioimmunoassay and receptor subtypes detected using ligands BQ123 and BQ3020. 812 Nov 79

Recent studies have shown that the basal release of PRL from anterior pituitary cells is inhibited by endothelin-1 (ET-1) and ET-3. To determine whether ET also regulates the synthesis and release of PRL by decidual cells, we examined the effects of ET on the synthesis and release of PRL from an enriched fraction of human decidual cells prepared by isopycnic centrifugation of enzymatically dispersed term decidual tissue. Exposure of decidual cells to ET-1 (10(-7) M) for 96 h caused a progressive decrease in basal PRL synthesis and release beginning 24 h after exposure with half-maximal inhibition occurring at an ET-1 concentration of 5 x 10(-9) M. Between 72-96 h of culture, ET-1-exposed cells synthesized 37.2 +/- 2.7% (SEM) and released 32.3 +/- 1.3% less PRL than control cells (P < 0.01). ET-1-exposed cells incubated with [35S]methionine between 72-96 h also released less [35S] PRL than control cells. Sarafotoxin S6C, an ETB receptor agonist, also inhibited basal PRL release, whereas BQ-123, an ETA receptor antagonist, had no effect on basal or on ET-1-mediated inhibition of PRL release. ET-1 also markedly inhibited the stimulation of PRL synthesis and release in response to insulin and insulin-like growth factor-1 (IGF-1). Cells exposed to insulin (100 ng/ml) and IGF-1 (50 ng/ml) alone released 61.2 +/- 3.6% and 40.0 +/- 3.8% more PRL, respectively, than control cells between 72-96 h of exposure. However, cells exposed simultaneously to insulin and ET-1 (10(-7) M) released only 17.1 +/- 3.5% more PRL than control cells during the same time period, and cells exposed simultaneously to IGF-1 and ET-1 released only 4.1 +/- 1.8% more PRL than controls during the same time interval (P vs. insulin or IGF-1 alone < 0.001 in each instance). Both basal and insulin- and IGF-1-stimulated PRL release were also inhibited by the ET isotypes ET-2 and ET-3, and by the ET-1 precursor, big ET. Since macrophages and decidual cells synthesize ET, and decidual tissue contains specific receptors for ET, the inhibitory action of ET on basal and stimulated PRL release may result from an autocrine and/or paracrine effect and appears to be mediated through the ETB receptor.
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PMID:Endothelin inhibits basal and stimulated release of prolactin by human decidual cells. 834 96

We investigated the vascular effects mediated by ETA and ETB receptors in human dorsal hand veins in vivo, using sarafotoxin S6c (SFTX6c) as a selective agonist of ETB receptors and endothelin-1 (ET-1) as a nonselective agonist of ETA and ETB receptors. The cyclo-oxygenase inhibitor aspirin and the nitric oxide synthase inhibitor L-NMMA were used to examine the modulating role of endothelial vasodilators on the response to SFTX6c. Drugs were all infused into the hand veins, at locally but not systemically active doses, via a 23 SWG butterfly cannula, with the exception of aspirin, which was administered orally. Hand vein size was measured by the Aellig technique. The study was performed in six healthy male subjects. Data (mean +/- SEM) were examined by ANOVA. Results are expressed as percent change from baseline at 60 min. ET-1 (5 pmol/min for 60 min) caused venoconstriction of 68 +/- 6% (p = 0.0001). SFTX6c at the same dose caused venoconstriction of 19 +/- 4% (p = 0.003). The response to SFTX6c was significantly less than to ET-1 (p = 0.002). Constriction to SFTX6c tended to increase when this agent was co-administered with aspirin (25 +/- 7%) or L-NMMA (24 +/- 10%) and was significantly potentiated when these agents were co-administered (45 +/- 4%; p = 0.01 vs. SFTX6c alone). We have demonstrated that the selective ETB agonist SFTX6c produces venoconstriction in human hand veins in vivo and that this venoconstriction is modulated by the generation of endothelium-derived vasodilators. In this vascular bed, venoconstriction rather than venodilatation appears to be the predominant effect of stimulation of ETB receptors with SFTX6c.
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PMID:Endothelium-dependent modulation of venoconstriction to sarafotoxin S6c in human veins in vivo. 858 56

By virtue of its exquisite sensitivity to the effects of endothelin-1 (ET-1), the kidney has been a consistent candidate for a pathophysiologic role for the endothelins. However, observed species differences in both receptor distribution and the subtypes mediating vasoconstriction have necessitated the development of a novel quantitative RT-PCR assay suitable for the direct investigation of human tissue, which is usually available only in very small amounts (i.e., biopsy specimens). In this study we quantified ETA and ETB receptor mRNA in normal renal cortex and medulla. For seven samples, cortex contained 0.19 +/- 0.10 amol ETA mRNA and 1.09 +/- 0.38 amol ETB mRNA/microgram total RNA (mean +/- SEM). In medulla these values were 0.47 +/- 0.25 and 2.17 +/- 1.90, respectively. The ratios of ETA to ETB were about 20:80, which correlates closely with previous studies of expressed receptor protein. This fluorescent nested quantitative RT-PCR assay provides a tool for further investigation of the human ET system at the molecular level in tissue from living individuals, and is of general applicability to the study of endogenous ligand-receptor systems.
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PMID:Comparative quantification of endothelin receptor mRNA in human kidney: new tools for direct investigation of human tissue. 858 85

The human kidney contains about 70% endothelin ETB receptors, with the remaining ETA subtype mainly localized to the vasculature. Our aim was to characterize new ligands using native human receptors present in this tissue. In competition binding assays, sections of kidney (n > or = 3 individuals, +/- SEM) were incubated with 100 pM [125I]ET-1 and increasing concentrations of unlabeled ligands. The nonpeptide antagonists inhibited [125I]ET-1 binding monophasically (bosentan, Kd 360 +/- 50 nM, Bmax 39.5 +/- 9.4 fmol/mg protein; SB209670, Kd 80.0 +/- 12.5 nM, Bmax 51.8 +/- 20.4 fmol/mg protein). The ETB agonist sarafotoxin S6c competed biphasically with 1,400-fold selectivity for the ETB subtype (Kd ETA 2.2 +/- 0.2 microM, Bmax 22.6 +/- 4.9 fmol/mg protein; Kd ETB 1.5 +/- 0.2 nM, Bmax 46.3 +/- 9.0 fmol/mg protein). In contrast, BQ788 (an ETB antagonist in animals) competed monophasically (Kd 125.9 +/- 10.3 nM) and is not selective for the human renal ETB receptor. The ETA-selective antagonist S97-139 competed biphasically, with high affinity and 1,100-fold selectivity for the ETA site (Kd ETA 4.4 +/- 4.0 nM), but low affinity for ETB receptors (Kd ETB 5.1 +/- 0.4 microM). Autoradiography showed that ETA-selective compounds inhibited [125I]ET-1 binding to the ETA receptors mediating vasoconstriction in blood vessels but spared ETB receptors, which in the human kidney may be involved in salt and water balance as well as clearing ET from the plasma.
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PMID:Characterization of peptide and nonpeptide antagonists in human kidney. 858 19

We have characterized the endothelin (ET) receptor subtypes present within normal human cerebral cortex (CC), glioblastoma multiforme (GBM), and meningiomas (MGs), using two subtype-selective radioligands, [125I]-PD151242 (ETA) and [125I]-BQ3020 (ETB). For saturation experiments, sections of tissue were incubated with increasing concentrations (8 pM-4 nM) of either [125I]-PD151242 or [125I]-BQ3020 in incubation buffer (22 degrees C, 2 h). In saturation binding assays, [125I]-PD151242 bound with high affinity to a single population of ET receptors (n = individuals; +/- SEM) in normal CC (n = 3; Kd 1.23 +/- 0.20 nM; Bmax 28.10 +/- 9.04 fmol/mg protein), GBM (n = 5; Kd 1.62 +/- 0.20 nM; Bmax 147.04 +/- 62.8 fmol/mg protein), and MGs (n = 3; Kd 3.10 +/- 0.44 nM; Bmax 290.3 +/- 105.8 fmol/mg protein). [125I]-BQ3020 also bound with high affinity to a single population of ET receptors in normal CC (n = 3; Kd 4.54 +/- 1.58 nM; Bmax 190.5 +/- 88.8 fmol/mg protein), GBM (n = 4; Kd 1.38 +/- 0.28 nM; Bmax 234.0 +/- 153.6 fmol/mg protein), and MGs (n = 3; Kd 0.25 +/- 0.09 nM; Bmax 22.8 +/- 18.0 fmol/mg protein). To determine receptor subtype localization, autoradiography was performed after incubation of sections with 0.1 nM [125I]-ET-1 (ETA and ETB), [125I]-PD151242 (ETA), and [125I]-BQ3020 (ETB). Autoradiography demonstrated a high concentration of ETA receptors within the pial and intraparenchymal vessels and meninges overlying the CC. Gray and white matter were diffusely ETB-positive. GBM had a strongly vascular pattern of ETA distribution. ETA receptors were dense and homogeneous in MGs. [125I]-PD151242 binds with high affinity to human pial and intraparenchymal vessels and is able to clearly delineate the microvasculature in GBM. Selective ETA receptor manipulation may have potential benefits in cerebrovascular disease and neoplasia without producing detrimental effects on the predominantly ETB-positive brain parenchyma.
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PMID:Characterization of endothelin receptors in human brain cortex, gliomas, and meningiomas. 858 29


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