- New fluorescent adenosine A1-receptor agonists that allow quantification of ligand-receptor interactions in microdomains of single living cells
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Fluorescence spectroscopy is becoming a valuable addition to the array of techniques available for scrutinizing ligand-receptor interactions in biological systems. In particular, scanning confocal microscopy and fluorescence correlation spectroscopy (FCS) allow the noninvasive imaging and quantification of these interactions in single living cells. To address the emerging need for fluorescently labeled ligands to support these technologies, we have developed a series of red-emitting agonists for the human adenosine A1-receptor that, collectively, are N6-aminoalkyl derivatives of adenosine or adenosine 5′-N-ethyl carboxamide. The agonists, which incorporate the commercially available fluorophore BODIPY [630/650], retain potent and efficacious agonist activity, as demonstrated by their ability to inhibit cAMP accumulation in chinese hamster ovary cells expressing the human adenosine A1-receptor. Visualization and confirmation of ligand-receptor interactions at the cell membrane were accomplished using confocal microscopy, and their suitability for use in FCS was demonstrated by quantification of agonist binding in small areas of cell membrane.
- Middleton, Richard J.,Briddon, Stephen J.,Cordeaux, Yolande,Yates, Andrew S.,Dale, Clare L.,George, Michael W.,Baker, Julian G.,Hill, Stephen J.,Kellam, Barrie
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p. 782 - 793
(2008/01/27)
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- Structure-Activity Relationships of N6-Benzyladenosine-5'-uronamides as A3-Selective Adenosine Agonists
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Adenosine analogues modified at the 5'-position as uronamides and/or as N6-benzyl derivatives were synthesized.These derivatives were examined for affinity in radioligand binding assays at the newly discovered rat brain A3 adenosine receptor and at rat brain A1 and A2a receptors. 5'-Uronamide substituents favored A3 selectivity in the order N-methyl > N-ethyl ca. unsubstituted carboxamide > N-cyclopropyl. 5'-(N-Methylcarboxamido)-N6-benzyladenosine was 37-56-fold more selective for A3 receptors.Potency at A3 receptors was enhanced upon substitution of the benzyl substituent with nitro and other groups. 5'-N-Methyluronamides and N6-(3-substitutedbenzyl)adenosines are optimal for potency and selectivity at A3 receptors.A series of 3-(halobenzyl)-5'-N-ethyluronamide derivatives showed the order of potency at A1 and A2a receptors of I ca.Br > Cl > F.At A3 receptors the 3-F derivative was weaker than the other halo derivatives. 5'-N-Methyl-N6-(3-iodobenzyl)adenosine displayed a Ki value of 1.1 nM at A3 receptors and selectivity versus A1 and A2a receptors of 50-fold.A series of methoxybenzyl derivatives showed that a 4-methoxy group best favored A3 selectivity.A 4-sulfobenzyl derivative was a specific ligand at A3 receptors of moderate potency.An aryl amino derivative was prepared as a probe for radioiodination and receptor cross-linking.
- Gallo-Rodriguez, Carola,Ji, Xiao-duo,Melman, Neli,Siegman, Barry D.,Sanders, Lawrence H.,et al.
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p. 636 - 646
(2007/10/02)
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- N6-substituted N-alkyladenosine-5'-uronamides: bifunctional ligands having recognition groups for A1 and A2 adenosine receptors.
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The coronary vasoactivity of N-ethyl-1'-deoxy-1'-(6-amino-9H-purin-9-yl)-beta-D-ribofuranuronamide (NECA, 1) is over 2 orders of magnitude greater than that of adenosine, and the vasoactivity of certain N6-substituted adenosines is as much as 1 order of m
- Olsson,Kusachi,Thompson,Ukena,Padgett,Daly
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p. 1683 - 1689
(2007/10/02)
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