title: 2-[2-[4-[2-[2-[ 1,3-Dihydro- 1,1-bis (4-hydroxyphenyl)-3-oxo-5-isobenzofuranthioureidyl]ethylaminocarbonyl]ethyl]phenyl] ethylamino]-5'-N-ethylcarboxamidoadenosine (FITC-APEC): A Fluorescent Ligand For A2a-Adenosine Receptors.
abstract: The fluorescein conjugate, FITC-APEC (2-[2-[4-[2-[2-[1,3-dihydro-l,l-bis(4-hydroxyphenyl)-3-oxo-5-isobenzofuranthioureidyl]ethylaminocarbonyl]ethyl]phenyl]ethylamino]-5'-N-ethylcarboxamidoadenosine), is a novel ligand derived from a series of functionalized congeners that act as selective A2a-adenosine receptor agonists. The binding of FITC-APEC to bovine striatal A2a,-adenosine receptors measured by fluorescence techniques was saturable and of a high affinity, with aBmax, of 2.3 ± 0.3 pmol/mg protein andKDof 57 ± 2 nM. TheKDvalue estimated by fluorescence was consistent with theKi(11 ± 0.3 nM) obtained by competition studies with [3H]CGS 21680. Additionally, theBmax, value found by FITC-APEC measurement was in agreement withBmax, values obtained using radioligand binding. FITC-APEC exhibited rapid and reversible binding to bovine striatum. The potencies of chemically diverse A2a-adenosine receptor ligands estimated by inhibition of FITC-APEC binding were in good agreement with their potencies determined using radioligand binding techniques (r= 0.97,P= 0.0003). FITC-APEC binding was not altered by purine derivatives that do not recognize A2a-adenosine receptors. These findings demonstrate that the novel fluorescent ligand FITC-APEC can be used in the quantitative characterization of ligand binding to A2a-adenosine receptors.
authors.affiliation: Laboratory for Neuroscience, Pharmaceutical Discovery Corporation, 7 Westchester Plaza, Elmsford, New York 10523.
authors.forename: R Tyler
authors.initials: RT
authors.lastname: McCabe
authors.forename: Phil
authors.initials: P
authors.lastname: Skolnick
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Jacobson
keywords: A2a-adenosine receptors; Fluorescence; bovine striatum; receptor binding