title: Agonist derived molecular probes for A2 adenosine receptors.
abstract: The adenosine agonist 2-(4-(2-carboxyethyl)phenylethylamino)-5'-N- ethylcarboxamidoadenos ine (CGS21680) was recently reported to be selective for the A2 adenosine receptor subtype, which mediates its hypotensive action. To investigate structure/activity relationships at a distal site, CGS21680 was derivatized using a functionalized congener approach. The carboxylic group of CGS21680 has been esterified to form a methyl ester, which was then treated with ethylenediamine to produce an amine congener. The amine congener was an intermediate for acylation reactions, in which the reactive acyl species contained a reported group, or the precursor for such. For radioiodination, derivatives of p-hydroxyphenylpropionic, 2-thiophenylacetic, and p-aminophenylacetic acids were prepared. The latter derivative (PAPA-APEC) was iodinated electrophilically using [125I]iodide resulting in a radioligand which was used for studies of competition of binding to striatal A2 adenosine receptors in bovine brain. A biotin conjugate and an aryl sulfonate were at least 350-fold selective for A2 receptors. For spectroscopic detection, a derivative of the stable free radical tetramethyl-1-piperidinyloxy (TEMPO) was prepared. For irreversible inhibition of receptors, meta- and para-phenylenediisothiocyanate groups were incorporated in the analogs. We have demonstrated that binding at A2 receptors is relatively insensitive to distal structural changes at the 2-position, and we report high affinity molecular probes for receptor characterization by radioactive, spectroscopic and affinity labelling methodology.
authors.affiliation: National Institute of Diabetes, and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
authors.forename: K A
authors.initials: KA
authors.lastname: Jacobson
authors.forename: L K
authors.initials: LK
authors.lastname: Pannell
authors.forename: X D
authors.initials: XD
authors.lastname: Ji
authors.forename: M F
authors.initials: MF
authors.lastname: Jarvis
authors.forename: M
authors.initials: M
authors.lastname: Williams
authors.forename: A J
authors.initials: AJ
authors.lastname: Hutchison
authors.forename: W W
authors.initials: WW
authors.lastname: Barrington
authors.forename: G L
authors.initials: GL
authors.lastname: Stiles
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives*; D000262:Adenylyl Cyclases / Q000032:analysis; D000818:Animals; D001667:Binding, Competitive; D001792:Blood Platelets / Q000378:metabolism; D001921:Brain / Q000378:metabolism; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D002851:Chromatography, High Pressure Liquid; D000242:Cyclic AMP / Q000378:metabolism; D006801:Humans; D007457:Iodine Radioisotopes; D015335:Molecular Probes; D010627:Phenethylamines; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D011983:Receptors, Purinergic / Q000032:analysis*; D013329:Structure-Activity Relationship
chemical_list: D007457:Iodine Radioisotopes; D015335:Molecular Probes; D010627:Phenethylamines; D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D000241:Adenosine