ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: The A2a adenosine receptor agonist 2-[2-(4-amino-3-iodophenyl)ethylamino]adenosine is a potent coronary vasodilator. The corresponding radioiodinated ligand, [125I]APE, discriminates between high- and low-affinity conformations of A2a adenosine receptors. In this study, [125I]APE was used for rapid (24-h) autoradiography in rat brain sections. The pattern of [125I]APE binding is consistent with that expected of an A2a-selective radioligand. It is highest in striatum, nucleus accumbens, and olfactory tubercle, with little binding to cortex and septal nuclei. Specific [125I]APE binding to these brain regions is abolished by 1 µM 2-p-(2-carboxyethyl)phenethylamino-5′-N-ethylcarboxamidoadenosine (CGS-21680) but is little affected by 100 nM 8-cyclopentyl-1,3-dipropylxanthine. Conversion of [125I]APE to the corresponding arylazide results in [125I]AzPE. The rank-order potency of compounds to compete for [125I]AzPE binding in the dark is CGS-21680 〉 d-(R)-N6-phenylisopropyladenosine 〉 N6-cyclopentyladenosine, indicating that it also is an A2a-selective ligand. Specific photoaffinity labeling by [125I]AzPE of a single polypeptide (42 kDa) corresponding to A2a adenosine receptors is reduced 55 ± 4% by 100 µM guanosine 5′-O-(3-thiotriphosphate) and 91 ± 1.3% by 100 nM CGS-21680. [125I]APE and [125I]AzPE are valuable new tools for characterizing A2a adenosine receptors and their coupling to GTP-binding proteins by autoradiography and photoaffinity labeling.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1471-4159.1995.65052072.x
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