Evidence for a novel angiotensin II receptor involved in angiogenesis in chick embryo chorioallantoic membrane

1993 ◽  
Vol 264 (2) ◽  
pp. R460-R465 ◽  
Author(s):  
F. A. Le Noble ◽  
N. H. Schreurs ◽  
H. W. van Straaten ◽  
D. W. Slaaf ◽  
J. F. Smits ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Chick Embryo ◽  
Binding Sites ◽  
Radioligand Binding ◽  
Chorioallantoic Membrane ◽  
Affinity Constant ◽  
Binding Studies ◽  
At1 Antagonist ◽  
Radioligand Binding Studies ◽  
At2 Receptors

Angiotensin II acts as a growth factor in the cardiovascular system and has been implicated in angiogenesis. The existence of at least two types of angiotensin II receptors, the AT1 and the AT2 receptors, has been suggested by ligand binding studies. We used three different AT receptor antagonists to study the receptor mediating angiotensin II-induced angiogenesis in the chorioallantoic membrane (CAM) of the chick embryo. Angiotensin II caused pronounced angiogenesis of pre- and postcapillary vessels of 30-40%. This response could only be blocked by adding the peptidergic AT2 antagonist CGP-42112A. The nonpeptidergic AT2 antagonist PD123319 and AT1 antagonist losartan (DuP 753) were not effective. In addition, we used radioligand binding studies with a range of ligands to define the nature of the receptor. Our results show a high density of specific single class AT receptor with a total number of binding sites of 1,190 fmol/mg protein and an affinity constant for angiotensin II of 2.7 nM. The inhibitory concentrations (IC50) for CGP-42112A, PD 123319 and losartan were 724, > 100,000, and 59,000 nM, respectively. Our studies suggest that these binding sites act as receptors for angiotensin II-induced angiogenesis. Both functional and radioligand binding studies suggest that the receptor is different from the classical mammalian AT1 and AT2 receptors.

α1-Adrenoceptor subtypes on rat afferent arterioles assessed by radioligand binding and RT-PCR

2001 ◽  
Vol 281 (1) ◽  
pp. F172-F178 ◽  
Author(s):  
Max Salomonsson ◽  
Melinda Oker ◽  
Susan Kim ◽  
Hua Zhang ◽  
James E. Faber ◽  
...  
Keyword(s):  
Binding Sites ◽  
Radioligand Binding ◽  
Rt Pcr ◽  
Binding Studies ◽  
Single Class ◽  
Site Model ◽  
Adrenoceptor Antagonist ◽  
Resistance Vessels ◽  
Afferent Arterioles ◽  
Radioligand Binding Studies

We utilized [3H]prazosin saturation and competition radioligand binding studies to characterize the expression of α1-adrenoceptors in preglomerular vessels. mRNA for adrenoceptor subtypes was assayed using RT-PCR. The vessels were isolated using an iron oxide-sieving method. [3H]prazosin bound to a single class of binding sites ( K d0.087 ± 0.012 nM, Bmax 326 ± 56 fmol/mg protein). Phentolamine displaced [3H]prazosin (0.2 nM) with a p K i of 8.37 ± 0.09. Competition with the selective α1A-adrenoceptor antagonist 5-methylurapidil fit a two-site model (p K i9.38 ± 0.21 and 7.04 ± 0.15); 59 ± 3% of the sites were high-affinity, and 41 ± 3% were low-affinity binding sites. Competition with the α1D-adrenoceptor antagonist 8-(2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl)-8-azaspiro[4.5]decane-7,9-dione dihydrochloride (BMY-7378) fit a one-site model with low affinity (p K i 6.83 ± 0.03). The relative contents of α1A-, α1B-, and α1D-adrenoceptor mRNAs were 64 ± 5, 25 ± 5, and 11 ± 1%, respectively. Thus there was a very good correlation between mRNA and receptor binding for the subtypes. These data indicate a predominance of the α1A-adrenoceptor subtype in rat renal resistance vessels, with smaller densities of α1B- and α1D-adrenoceptors.

scholarly journals Enhanced responsiveness of endothelium in the growing/motile state to tumor necrosis factor/cachectin.

1989 ◽  
Vol 170 (3) ◽  
pp. 913-931 ◽  
Author(s):  
H Gerlach ◽  
H Lieberman ◽  
R Bach ◽  
G Godman ◽  
J Brett ◽  
...  
Keyword(s):  
Endothelial Cell ◽  
Binding Sites ◽  
Cell Shape ◽  
Radioligand Binding ◽  
Cell Binding ◽  
Binding Studies ◽  
Endothelial Cell Surface ◽  
High Affinity ◽  
Radioligand Binding Studies

Some in vivo observations have suggested that growing or perturbed endothelium, such as that which occurs during angiogenesis, is more sensitive to the action of cytokines (TNF/cachectin, TNF, or IL-1) than normal quiescent endothelial cells. This led us to examine the responsiveness of endothelium to TNF as a function of the growth/motile state of the cell. TNF-induced modulation of endothelial cell surface coagulant function was half-maximal at a concentration of approximately 0.1 nM in subconfluent cultures, whereas 1-2 nM was required for the same effect in postconfluent cultures. Perturbation of endothelial cell shape/cytoskeleton was similarly more sensitive to TNF in subconfluent cultures. Consistent with these results, radioligand binding studies demonstrated high affinity TNF binding sites, Kd approximately 0.1 nM on subconfluent cultures, whereas only lower affinity sites (Kd approximately 1.8 nM) were detected on postconfluent cultures. The mechanisms underlying this change in the affinity of endothelium for TNF were studied in four settings. Crosslinking experiments with 125I-TNF and endothelium showed additional bands corresponding to Mr approximately 66,000 and approximately 84,000 with subconfluent cultures that were not observed with postconfluent cultures. Experiments with X-irradiated endothelium, whose growth but not motility was blocked, indicated that proliferation was not required for induction of high affinity TNF sites. Postconfluent endothelium, triggered to enter the proliferative cycle by microbutuble poisons, expressed high affinity TNF binding sites together with changes in cell shape/cytoskeleton well before their entry into S phase. Using wounded postconfluent monolayers, cells that migrated into the wound and those close to the wound edge displayed enhanced TNF binding and modulation of coagulant properties. These results suggest a model for targetting TNF action within the vasculature; regulation of high affinity endothelial cell binding sites can direct TNF to activated cells in particular parts of the vascular tree.

Thymosthenic Agents, A Novel Approach in the Treatment of Schizophrenia

1989 ◽  
Vol 155 (S5) ◽  
pp. 33-36 ◽  
Author(s):  
Yves G. Gelders
Keyword(s):  
Binding Sites ◽  
Psychotic Disorders ◽  
Radioligand Binding ◽  
Receptor Subtypes ◽  
Binding Studies ◽  
Novel Approach ◽  
Definition Of ◽  
Radioligand Binding Studies ◽  
Β Adrenergic Receptors ◽  
The Brain

The pharmacotherapy of psychotic disorders which started in 1952, based on empirical results obtained with chlorpromazine by Delay & Deniker, has revolutionised the treatment of psychiatric diseases of non-organic origin. The discovery of haloperidol by Janssen in 1959 represented further progress in this field, since this was found to be more potent and to have generally less disturbing adverse effects than chlorpromazine. Nevertheless it took several years before dopamine-antagonism was put forward as possible mechanism of action for neuroleptic drugs (Carlsson & Lindqvist, 1963). From the early 1970s, however, the advent of radioligand binding studies provided new tools for studying neurotransmitter receptors in the brain and for investigating the interaction of drugs with various receptors. This technique allowed identification of receptor-binding sites related to pharmacologically defined receptors and receptor subtypes, e.g. α and β-adrenergic receptors. It also led to further subclassification and refined definition of receptors, e.g. dopamine-D1 and -D2, and different pharmacological effects mediated by the receptor subtypes have been identified.

scholarly journals Binding Affinity of Candesartan, Losartan, Telmisartan and Valsartan with Angiotensin II Receptor 1 Subtype

2013 ◽  
Vol 16 (1) ◽  
pp. 10-14 ◽  
Author(s):  
Mohiuddin Ahmed Bhuiyan ◽  
Mohammad Shahriar ◽  
Takafumi Nagatomo
Keyword(s):  
Angiotensin Ii ◽  
Binding Affinity ◽  
Binding Sites ◽  
Radioligand Binding ◽  
Pharmaceutical Journal ◽  
Angiotensin Ii Receptor ◽  
Binding Studies ◽  
At1 Receptors ◽  
At1 Antagonists ◽  
Number Of Binding Sites

This study was designed to examine the interaction in the binding of selective angiotensin II receptor antagonists towards angiotensin II type 1 receptor. The AT1 antagonists used in this study were valsartan, candesartan and losartan. Wild type AT1 receptors were transiently expressed in COS-7 cells and the expressed protein was isolated. The binding affinities of agonist and these four AT1 antagonists were determined towards AT1 receptors with the help of radioligand binding studies. The binding affinity of candesartan has been found to be maximum having a pKi value of 8.61±0.21 whereas losartan showed lowest binding affinity among the antagonists (pKi=7.17±0.07). Telmisartan also showed high (pKi=8.19±0.04) and valsartan had moderate binding affinity (pKi=7.65±0.12) towards AT1 receptors. The results of the study suggested that candesartan interacts very strongly with the receptor which is consistent with the maximum number of binding sites of in the chemical structure of candesartan. On the other hand, losartan has lower number of binding sites with the amino acid residues of AT1 receptor and as a result it showed the minimum affinity towards the receptor. DOI: http://dx.doi.org/10.3329/bpj.v16i1.14484 Bangladesh Pharmaceutical Journal 16(1): 10-14, 2013

Bronchospasmolytic and Adenosine Binding Activity of 8- (Proline / Pyrazole)-Substituted Xanthine Derivatives

2020 ◽  
Vol 17 ◽  
Author(s):  
Sneha Singh ◽  
Madhwi Ojha ◽  
Divya Yadav ◽  
Sonja Kachler ◽  
Karl-Norbert Klotz ◽  
...  
Keyword(s):  
Binding Affinity ◽  
Radioligand Binding ◽  
Binding Activity ◽  
Receptor Subtypes ◽  
Significant Protection ◽  
Binding Studies ◽  
Standard Drug ◽  
Xanthine Derivatives ◽  
Radioligand Binding Studies ◽  
Micromolar Range

Background: ABSTRACT: Background: 8-Phenyltheophylline derivatives exhibit prophylactic effects at a specific dose but do not produce the cardiovascular or emetic side effects associated with xanthines, thereby exhibiting unique characteristics of potential therapeutic importance. Methods: Novel series of 8-(proline/pyrazole)-substituted xanthine analogs has been synthesized. The affinity and selectivity of compounds to adenosine receptors have been assessed by radioligand binding studies. The synthesized compounds also showed good bronchospasmolytic properties (increased onset of bronchospasm; decreased duration of jerks) with 100% survival of animals in comparison to the standard drug. Besides, compound 8f & 9f showed good binding affinity in comparison to other synthesized compounds in the micromolar range. Results: The maximum binding affinity of these compounds was observed for A2B receptors, which is ~ 7 or 10 times higher as compared to A1, A2A and A3 receptors. The newly synthesized derivatives 8f, 9a-f, 17g-m, and 18g-m displayed significant protection against histamine aerosol induced bronchospasm in guinea pigs. Conclusion: Newly synthesized proline/pyrazole based xanthines compounds showed a satisfactory binding affinity for adenosine receptor subtypes. Replacement or variation of substituted proline ring with substituted pyrazole scaffold at 8thposition of xanthine moiety resulted in the reduction of adenosine binding affinity and bronchospasmolytic effects.

Radioligand Binding Studies on the Nucleoside Transport Protein

1991 ◽  
pp. 411-414
Author(s):  
Ad P. Ijzerman ◽  
Armand Voorschuur ◽  
Marieke Kruidering ◽  
Irene M. Pirovano ◽  
Herman Van Belle ◽  
...  
Keyword(s):  
Radioligand Binding ◽  
Transport Protein ◽  
Nucleoside Transport ◽  
Binding Studies ◽  
Radioligand Binding Studies

scholarly journals Identification of the angiotensin II receptor in rat mesenteric artery

1984 ◽  
Vol 223 (3) ◽  
pp. 659-671 ◽  
Author(s):  
J McQueen ◽  
G D Murray ◽  
P F Semple
Keyword(s):  
Angiotensin Ii ◽  
Binding Sites ◽  
Radioligand Binding ◽  
Specific Binding ◽  
Divalent Cations ◽  
Target Tissue ◽  
Angiotensin Ii Receptor ◽  
High Affinity ◽  
Rat Mesentery ◽  
Rat Mesenteric Artery

Specific binding sites of high affinity and low capacity for 125I-angiotensin II have been identified in a membrane fraction derived from arterial arcades of the rat mesentery. Heterogeneity of binding sites and extensive tracer degradation necessitated the use of nonlinear regression methods for the analysis of radioligand binding data. Forward and reverse rate constants for the high affinity sites obtained by three experimental approaches were in good agreement and gave a dissociation equilibrium constant (Kd) of 19-74 pM (95% confidence interval). Affinities for a number of angiotensin-related peptides calculated from competitive binding curves were in the order 125I-angiotensin II = angiotensin II greater than angiotensin III greater than [Sar1,Ile8]angiotensin II greater than [Sar1,Gly8]angiotensin II. Angiotensin I and biochemically unrelated peptides had virtually no effect on binding of tracer angiotensin II. The divalent cations Mn2+, Mg2+ and Ca2+ stimulated 125I-angiotensin II binding at concentrations of 2-10 mM, as did Na+ at 50-100 mM. In the presence of Na+ or Li+, K+ had a biphasic effect. The chelating agents EDTA and EGTA were inhibitory, as were the thiol reagents dithiothreitol and cysteine. This study defined angiotensin II binding sites in a vascular target tissue of sufficiently high affinity to interact rapidly with plasma angiotensin II at physiological concentrations.

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