Endothelin-1 conversion and receptor characterization in human placental arteries

1994 ◽  
Vol 267 (2) ◽  
pp. E242-E249
Author(s):  
B. M. Wilkes ◽  
C. M. Macica ◽  
P. F. Mento
Keyword(s):  
Blood Vessels ◽  
Competitive Inhibition ◽  
Polyacrylamide Gel Electrophoresis ◽  
Receptor Subtype ◽  
Scatchard Analysis ◽  
Binding Studies ◽  
Single Class ◽  
Endothelin 1 ◽  
Active Peptide ◽  
Receptor Sites

Endothelin-1-(1-21), a potent pressor peptide, is transcribed as big endothelin-(1-38) and converted to active peptide by endothelin-converting enzyme. The current investigation tested the hypothesis that human fetoplacental blood vessels convert big endothelin-1 to active peptide and that fetoplacental blood vessels respond to endothelin-1 by binding of the peptide to specific receptor sites. In the isolated perfused placental cotyledon the addition of big endothelin-1 to the perfusate caused a time-dependent increase in perfusion pressure that corresponded to the appearance of endothelin-1 in the perfusate. The properties of human placental endothelin-1 receptors were defined in binding studies performed on a plasma membrane fraction of small arteries (<1.0 mm) dissected from the placenta. Binding was saturable, reached steady state by 3 h at 25 degrees C, and was linear with protein concentration. Scatchard analysis of binding data indicated a single class of high-affinity binding sites with a dissociation constant of 27.6 +/- 2.3 pM and a density of 856 +/- 119 fmol/mg protein (n = 5). The potency order for competitive inhibition of the binding of 125I-labeled endothelin-1 [endothelin-1 = endothelin-2 > endothelin-3 = sarafotoxin S6b >> big endothelin-1 (human) = big endothelin-1 (porcine)] is most consistent with a type A endothelin receptor subtype. Phenylephrine, bradykinin, norepinephrine, atrial natriuretic factor, diltiazem, U-46619, and angiotensin II did not displace 125I-endothelin-1 binding. Endothelin receptors were shown to have an approximate molecular weight of 36,600 by polyacrylamide gel electrophoresis.(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelin receptors in human placenta: relationship to vascular resistance and thromboxane release

1990 ◽  
Vol 258 (5) ◽  
pp. E864-E870
Author(s):  
B. M. Wilkes ◽  
P. F. Mento ◽  
A. M. Hollander ◽  
M. E. Maita ◽  
S. Sung ◽  
...  
Keyword(s):  
Vascular Resistance ◽  
Human Placenta ◽  
Competitive Inhibition ◽  
Scatchard Analysis ◽  
Binding Studies ◽  
Single Class ◽  
Endothelin 1 ◽  
Binding Data ◽  
Endothelin 3

This investigation was performed to study the potential role of endothelin in the modulation of fetoplacental vascular resistance in the human placenta. Full-term placentas from uncomplicated pregnancies were studied within 30 min of delivery. The umbilical artery and vein to a single placental cotyledon were cannulated and the artery perfused with RPMI media (0.82 ml/min). Endothelin 1 caused a sustained dose-dependent increase in perfusion pressure. Infused endothelin 1 (50 nM) stimulated thromboxane release 2.3-fold compared with basal values. Thromboxane release persisted for 15 min after discontinuation of endothelin. Properties of human placental endothelin 1 receptors were defined in binding studies performed on a crude membrane fraction of placental cotyledons. Binding was saturable, reached steady state by 3 h at 25 degrees C, and was linear with protein concentration. Scatchard analysis of binding data indicated a single class of high-affinity binding sites with a Kd of 36.1 +/- 9.7 pM and a density of 185.4 +/- 9.6 fmol/mg protein (n = 5). The potency order for competitive inhibition of the binding of 125I-labeled endothelin 1 was endothelin 1 greater than endothelin 2 = endothelin 3 = sarafotoxin S6b greater than big endothelin (human) = big endothelin (porcine). Phenylephrine, bradykinin, norepinephrine, atrial natriuretic factor, diltiazem, U46619, and angiotensin II did not displace 125I-endothelin 1 from its receptors. These experiments demonstrate that endothelin 1 is a potent pressor substance in the human fetoplacental cotyledon. Pressor effects of endothelin may be mediated by a combination of direct effects and stimulation of vasoconstrictor prostanoids.

Evidence for functional thromboxane A2-prostaglandin H2 receptors in human placenta

1989 ◽  
Vol 256 (2) ◽  
pp. E256-E263
Author(s):  
A. Hedberg ◽  
P. F. Mento ◽  
E. C. Liu ◽  
A. M. Hollander ◽  
B. M. Wilkes
Keyword(s):  
Human Placenta ◽  
Radioligand Binding ◽  
Specific Binding ◽  
Scatchard Analysis ◽  
Binding Studies ◽  
Single Class ◽  
Receptor Sites ◽  
H2 Receptors ◽  
Placental Membranes

The aim of this investigation was to study the role of thromboxane (TX) A2 in the modulation of human fetoplacental vascular resistance. By use of the isolated perfused fetoplacental cotyledon, TX generation (measured by direct radioimmunoassay of TXB2) was demonstrated on the fetal side of the placental circulation. The stable TX mimetic U-46619 caused a dose-dependent increase in perfusion pressure that was inhibited by the TX receptor antagonist SQ 29548. To further characterize the putative TXA2-prostaglandin H2 receptors, binding studies were performed in placental membranes using [3H]SQ 29548. Kinetic analysis revealed rapid and reversible specific binding of [3H]SQ 29548. Saturation binding and Scatchard analysis indicated radioligand binding to a single class of receptors (dissociation constant, 9.11 +/- 0.60 nM; receptor density, 103 +/- 8 fmol/mg protein, n = 4). Prostaglandins D2, E1, E2, F2a, and I2 did not inhibit the specific binding of [3H]SQ 29548 at concentrations less than or equal to 10 microM. This study demonstrates that the human placenta produces and releases TXA2, which can act locally via specific receptor sites to constrict the fetoplacental vasculature.

Affinity chromatography purification and partial characterization of phytohemagglutinin-receptor glycoproteins from porcine splenic lymphocytes

1985 ◽  
Vol 63 (9) ◽  
pp. 932-940 ◽  
Author(s):  
Gilles Dupuis ◽  
Jean-Pierre Doucet ◽  
Bânû Bastin ◽  
Jeannine Cardin
Keyword(s):  
Affinity Chromatography ◽  
Competitive Inhibition ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Interleukin 2 ◽  
Lymphocyte Activation ◽  
Scatchard Analysis ◽  
Dependent Manner ◽  
Murine Cell Line ◽  
Lymphocyte Cultures

We describe the isolation of pig spleen lymphocyte glycoproteins that interact with phytohemagglutinin (PHA), the lectin from Phaseolus vulgaris. Purification was achieved by affinity chromatography of a Nonidet P-40 extract of the cells on a PHA – Affi-Gel 10 column. The retained glycoproteins were eluted with an acidic (pH 3.0) glycine buffer and represented 1.9–2.4% of the amount of protein applied to the column. They contained 20 ± 1.3% hexose and 1.7 ± 0.7% fatty acids, on a weight basis. Electrophoretic analyses (sodium dodecyl sulfate – polyacrylamide gel electrophoresis) showed the presence of major Coomassie blue positive bands with apparent molecular masses of 50–55, 75, 95, 130, and 155 kdaltons along with minor bands of 20–40, 42, 45, 60–65, 175, and 200–250 kdaltons. The purified PHA-receptor glycoproteins inhibited, in a dose-dependent manner, the incorporation of [3H]thymidine in pig lymphocytes cultured at a concentration of 106 cells/mL in the presence of PHA. A 50% inhibition was observed when 20 μg/mL of the glycoproteins was added to the lymphocyte cultures containing 0.5 μg/mL of PHA. Scatchard analysis of the binding of 125I-labelled PHA, in the presence of increasing amounts of the purified glycoproteins, showed a suppression of the binding of the lectin to high affinity sites of the cells, as evidenced by a change from biphasic to a linear profile. Results of binding suggested a competitive inhibition by a population of purified glycoproteins with a similar affinity for the lectin. The purified glycoproteins decreased PHA-dependent interleukin 2 (IL-2) production by pig lymphocytes as assayed with a IL-2 dependent murine cell line. It is suggested that the affinity-purified PHA-reactive glycoproteins are inhibitors of PHA-dependent cellular responses because they compete with PHA-receptor sites on the lymphocyte plasma membrane. A mouse antiserum raised against the purified glycoproteins inhibited PHA-induced lymphocyte activation, but did not stimulate lymphocytes when added alone to lymphocyte cultures or in combination with a antimouse antiserum.

Characterization of glomerular thromboxane receptor sites in the rat

1989 ◽  
Vol 256 (6) ◽  
pp. F1111-F1116 ◽  
Author(s):  
B. M. Wilkes ◽  
J. Solomon ◽  
M. Maita ◽  
P. F. Mento
Keyword(s):  
Specific Binding ◽  
Binding Studies ◽  
Single Class ◽  
Thromboxane Receptor ◽  
Renal Glomeruli ◽  
Receptor Sites ◽  
High Affinity Receptor ◽  
Pg E2 ◽  
Txa2 Receptor Antagonist

The aim of this study was to identify and characterize thromboxane (Tx) receptor sites in renal glomeruli. Binding studies were performed on freshly isolated glomeruli using the stable TxA2 receptor antagonist, [3H]SQ 29548. Specific binding was saturable, reversible, and varied with glomerular protein. Scatchard plots revealed a single class of high-affinity receptor sites (Kd = 14.3 +/- 2.4 nM, Bmax = 361 +/- 22 fmol/mg; n = 5). Specific binding was inhibited by Tx agonists (U-46619 and U-44069) and antagonist (SQ 29548) and was highly specific for Tx, since prostaglandin (PG)E2 and PGF2 alpha were 1,000-fold less potent in inhibiting binding. In vivo, U-46619 (1.75 micrograms.kg-1.min-1) was without effect on mean arterial pressure, but reduced renal blood flow by 71% (P less than 0.01) and glomerular filtration rate by 67% (P less than 0.01) and increased filtration fraction by 24% (P less than 0.05). SQ 29548 (10 micrograms.kg-1.min-1) completely blocked the renal effects of U-46619. These studies demonstrate the presence of specific receptor sites for Tx on renal glomeruli that are linked to modulation of renal hemodynamics.

scholarly journals Overexpression of the insulin-like growth factor I receptor in human pheochromocytomas

2006 ◽  
Vol 36 (2) ◽  
pp. 279-287 ◽  
Author(s):  
Christian Fottner ◽  
Timo Minnemann ◽  
Sarah Kalmbach ◽  
Matthias M Weber
Keyword(s):  
Scatchard Analysis ◽  
Mrna Levels ◽  
Therapeutic Approaches ◽  
Binding Studies ◽  
Single Class ◽  
Normal Tissues ◽  
Igf System ◽  
Igf I ◽  
Polymerase Chain

In order to determine the role of the IGF-I receptor (IGF-IR) in human pheochromocytomas we have compared the expression of the IGF-IR in normal tissues and in pheochromocytomas with regard to the IGF-IR mRNA levels and ligand binding. By semiquantitative reverse transcription polymerase chain reaction (RT-PCR), the mRNA of the IGF-IR could be detected in all samples of normal adrenomedullary cells (n=13) and pheochromocytomas (n=16). However, pheochromocytomas exhibited 2.8-fold higher mean IGF-IR mRNA levels than normal adrenomedullary cells (2.8±0.5×105 molecules/μg RNA vs 7.8±1.2×105 molecules/μg RNA; P < 0.001). This overexpression of the IGF-IR in pheochromocytomas could be confirmed at the protein level by binding studies. Radioligand assays and Scatchard analysis revealed a single class of high affinity IGF-IR binding sites with a similar dissociation constant (Kd: 0.32±0.1 nmol/l vs 0.22±0.08 nmol/l) for both normal adrenomedullary cells and pheochromocytomas. However, specific 125I-labeled IGF-I binding and the calculated receptor concentration were significantly elevated in pheochromocytomas as compared with normal adrenomedullary cells (58.3±5 vs 24.3±12 nmol/kg protein; P < 0.05). In summary, our results demonstrate significant overexpression of the IGF-IR in human pheochromocytomas. This suggests a possible role of the IGF system in the pathogenesis of adrenal neoplasia and thus IGF-IR may be a target for future therapeutic approaches.

Cyclic adenosine 3′,5′-monophosphate binding protein in developing myxospores of Myxococcus xanthus

1980 ◽  
Vol 26 (8) ◽  
pp. 905-911 ◽  
Author(s):  
Michael Orlowski
Keyword(s):  
Binding Sites ◽  
High Speed ◽  
Binding Protein ◽  
Polyacrylamide Gel Electrophoresis ◽  
Myxococcus Xanthus ◽  
Protein Band ◽  
Specific Protein ◽  
Supernatant Fraction ◽  
Scatchard Analysis ◽  
Single Class

The interaction of cyclic adenosine 3′,5′-monophosphate (cAMP) with specific protein molecules was examined in the high-speed supernatant fraction of extracts made at stages throughout glycerol-induced myxospore development in Myxococcus xanthus. Experiments using 8-azido[32P]cAMP, a photoaffinity analogue of cAMP, and SDS – polyacrylamide gel electrophoresis showed that the nucleotide interacts with only a single protein band of 12 500 molecular weight. Both the identiy and amount of this protein remained constant throughout development. The binding protein was specific for cAMP; other nucleotides did not compete with cAMP for binding sites. A Scatchard analysis showed evidence of only a single class of binding sites with a high affinity for cAMP.

Evidence for existence of two distinct bradykinin receptors on rat mesangial cells

1993 ◽  
Vol 264 (3) ◽  
pp. F548-F556 ◽  
Author(s):  
J. L. Bascands ◽  
C. Pecher ◽  
S. Rouaud ◽  
C. Emond ◽  
J. L. Tack ◽  
...  
Keyword(s):  
Calcium Concentration ◽  
Mesangial Cells ◽  
Cell Counting ◽  
Scatchard Analysis ◽  
Binding Studies ◽  
Single Class ◽  
B1 Receptor ◽  
Heterologous Desensitization ◽  
Dose Dependent ◽  
Dissociation Constant Kd

We investigated the possible presence of bradykinin (BK) B1 receptor on rat mesangial cells (MC) by binding studies and by the effect of the B1 agonist des-Arg9-BK on intracellular calcium concentration ([Ca2+]i) and DNA synthesis in comparison with the effects of BK. Binding studies demonstrated specific, saturable binding for des-Arg9-[3H]BK inhibited by B1 but not by B2 antagonists. Scatchard analysis revealed a single class of B1 binding site with a maximum density of 15 fmol/mg protein and an affinity of 8.7 +/- 2.4 nM. Saturation and competition studies of 125I-[Tyr0]BK demonstrated the presence of two classes of B2 binding sites [dissociation constant (Kd) = 0.1 and 4 nM, respectively]. On fura-2-loaded adherent MC, both des-Arg9-BK and BK induced a biphasic increase (a transient enhancement followed by a sustained phase) in [Ca2+]i, both in primary culture and in cloned MC. Both the transient and sustained phases of [Ca2+]i induced by des-Arg9-BK were dose dependent, whereas BK induced a transient dose-dependent rise in [Ca2+]i, but the sustained phase remained constant. The increases in [Ca2+]i induced by des-Arg9-BK and BK were specifically abolished by B1 and B2 receptor antagonists, respectively, and showed homologous but not heterologous desensitization. Des-Arg9-BK and BK induced a significant proliferation (tested by cell counting and [3H]thymidine incorporation) of quiescent MC. Furthermore, the effects of des-Arg9-BK and BK were additive on Ca2+ mobilization but not on mitogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Human Platelets Possess an Inducible and Saturable Receptor Specific for Fibrinogen

1979 ◽  
Author(s):  
T.S. Edgington ◽  
G.A. Marguerie ◽  
E.F. Plow
Keyword(s):  
Polyacrylamide Gel Electrophoresis ◽  
Human Platelets ◽  
Scatchard Analysis ◽  
Single Class ◽  
Platelet Receptor ◽  
Per Se ◽  
Polypeptide Chains ◽  
Dissociation Constant Kd ◽  
Aggregation Phenomenon

Fibrinogen is required for ADP-dependent aggregation of human platelets; but the molecular basis for the requirement is not: known. Fibrinogen, rendered free of fibronectin, plasminogen, VIII, II and XIII, was radiolabelled (125I-fg) and used as the probe for a platelet receptor. Platelets were isolated by differential centrifugation, washed in calcium-free Tyrode’s solution containing 0.2% albumin and isolated by exclusion from Sepharose CL 2B. 125I-fg bound to platelets only after ADP stimulation, and binding was characteristic of a saturable receptor. Specificity was established by demonstration that fibrinogen completely inhibited binding of 125I-fg, competing with the same affinity, whereas other proteins were without effect. SDS polyacrylamide gel electrophoresis of the platelets after reduction demonstrated 125I polypeptide chains with migration identical to Aα, Bβ and γ chains; and fibrinopeptide A was on the bound 125I-fg indicating that fibrinogen per se is bound. Scatchard analysis of binding at optimal concentration of ADP (≥ 5 μM) indicated 4,644 ± 186 receptors with a dissociation constant Kd = 1.3 x 10-7 M, comparable to that estimated directly from the aggregation reactions. Receptors induced at different ADP concentrations appeared to have the same affinity for fibrinogen, indicating the probable existence of only a single class of receptors. We conclude that a specific saturable receptor is rapidly induced on human platelets by ADP, and postulate that this event may play a Significant role in the observed in vitro aggregation phenomenon and perhaps the primary hemostatic function of platelets. Supportedby NIH grant HL-16411.

scholarly journals Characterization of the high-affinity receptors on Swiss 3T3 cells which mediate the binding, internalization and degradation of the mitogenic peptide bombesin

1988 ◽  
Vol 252 (1) ◽  
pp. 227-235 ◽  
Author(s):  
K D Brown ◽  
M S Laurie ◽  
C J Littlewood ◽  
D M Blakeley ◽  
A N Corps
Keyword(s):  
Enzyme Inhibitors ◽  
Competitive Inhibition ◽  
Specific Binding ◽  
Scatchard Analysis ◽  
3T3 Cells ◽  
Single Class ◽  
High Affinity ◽  
Binding Data ◽  
Molecular Masses ◽  
Swiss 3T3

Bombesin and bombesin-related peptides such as gastrin-releasing peptide (GRP) stimulate DNA synthesis and proliferation of Swiss 3T3 cells in culture. We have used 125I-labelled [Tyr4]bombesin and 125I-labelled GRP to characterize and identify the receptors for these peptides on Swiss 3T3 cells. The binding of 125I-[Tyr4]bombesin, which retained full biological activity, was maximal between 20 and 30 min incubation at 37 degrees C, after which continued incubation led to a decline in cell-associated radioactivity. This decline was markedly slowed by the presence of lysosomal enzyme inhibitors. Specificity of the binding site was indicated by the competitive inhibition of binding by bombesin-related peptides, but not by unrelated peptides and growth factors. Scatchard analysis of binding data indicated a single class of high-affinity receptors. The calculated value for the dissociation constant (Kd) was 2.1 nM and each cell possesses approx. 240,000 receptors. Because [Tyr4]bombesin has no free amino group, 125I-GRP was used in chemical cross-linking studies. When disuccinimidyl suberate was used to covalently couple 125I-GRP to the cells, two major radiolabelled complexes were detected with molecular masses of approx. 80,000-85,000 and 140,000. The binding of 125I-[Tyr4]bombesin to the cells was pH-dependent with maximal binding at pH 6.5-7.5 and effectively no specific binding at pH values below 4.5. At 37 degrees C, cell-associated 125I-[Tyr4]bombesin quickly became resistant to removal by acidic buffers, suggesting its rapid transfer to an intracellular compartment. However, pre-incubation with unlabelled [Tyr4]bombesin did not induce down-regulation of bombesin receptors as measured by the subsequent binding of 125I-[Tyr4]bombesin. In contrast with the Swiss 3T3 cells, specific binding of 125I-[Tyr4]bombesin was not detectable in two cell lines which are biologically unresponsive to bombesin-related peptides.

scholarly journals Cyclosporine promotes glomerular endothelin binding in vivo.

1991 ◽  
Vol 1 (11) ◽  
pp. 1253-1258
Author(s):  
M Awazu ◽  
M Sugiura ◽  
T Inagami ◽  
I Ichikawa ◽  
V Kon
Keyword(s):  
Binding Sites ◽  
Competitive Inhibition ◽  
Hepatic Tissue ◽  
Binding Studies ◽  
Endothelin 1 ◽  
A Value ◽  
Equilibrium Dissociation ◽  
And Control ◽  
Dissociation Constant Kd

It has previously been shown that administration of cyclosporine causes a prompt (within 15 min after infusion) increase in circulating level of endothelin 1 and a pattern of glomerular hypoperfusion and hypofiltration which can be ameliorated with antiendothelin antibody. We now show that 60 min after cyclosporine, serum endothelin 1 level falls to less than 2.55 +/- 0.31 pg/mL (N = 6), a value comparable to that found in normal animals (less than 2 pg/mL). The study presented here also examines whether sustained cyclosporine-induced glomerular dysfunction is associated with altered endothelin receptor characteristics. Saturation and competitive inhibition binding studies in isolated glomerular membranes showed two binding sites. Of these, the density of the low-affinity site was affected by cyclosporine treatment (851 +/- 117 versus 425 +/- 61 fmol/mg of protein; P less than 0.05; N = 6) without a change in equilibrium dissociation constant, KD. The high-affinity site was not affected. The receptor characteristics of another vasoconstrictor, angiotensin II, were not affected by cyclosporine. In addition, there was no difference in endothelin binding sites in hepatic tissue between cyclosporine and control rats. These results raise the intriguing possibility that cyclosporine-induced glomerular dysfunction involves upregulation of endothelin binding sites and that altered endothelin receptors appear specific to the kidney.

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