title: The adenosine receptors present on the plasma membrane of chromaffin cells are of the A2b subtype.
abstract: The adenosine receptors in the plasma membrane of chromaffin cells from bovine adrenal medulla were characterized. The presence of A1 receptors was discounted owing to the absence of R-[3H]phenylisopropyladenosine (R-PIA) and [3H]8-cyclopentyl-1,3-dipropylxanthine ([3H]-DPCPX) binding. The binding of the specific A2a ligand CGS-21680 was low. In contrast, the binding of 5'-(N-[3H]-ethylcarboxamidoadenosine ([3H]NECA) was relatively high (1.7 pmol/mg of protein at a ligand concentration up to 90 nM). This binding did not correspond to non-adenosine receptor NECA binding sites because the specific [3H]-NECA binding was similar when unlabeled adenosine, NECA, or R-PIA was used to measure the nonspecific binding. The rank order of potency of different ligands for the displacement of specific [3H]NECA binding was DPCPX greater than NECA greater than chloroadenosine greater than R-PIA greater than theophylline = CGS-21680. These results indicate that the receptors present on the plasma membrane of chromaffin cells are exclusively of the A2b subtype.
authors.affiliation: Departament de Bioquimica i Fisiologia, Unitat de Bioquimica i Biologia Molecular A. Martí i Franquès 1, Barcelona, Spain.
authors.forename: V
authors.initials: V
authors.lastname: Casadó
authors.forename: T
authors.initials: T
authors.lastname: Casillas
authors.forename: J
authors.initials: J
authors.lastname: Mallol
authors.forename: E I
authors.initials: EI
authors.lastname: Canela
authors.forename: C
authors.initials: C
authors.lastname: Lluis
authors.forename: R
authors.initials: R
authors.lastname: Franco
mesh_terms: D015762:2-Chloroadenosine / Q000378:metabolism; D000241:Adenosine / Q000031:analogs & derivatives / Q000378:metabolism; D019830:Adenosine-5'-(N-ethylcarboxamide); D000818:Animals; D002417:Cattle; D002458:Cell Fractionation; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D002838:Chromaffin System / Q000737:chemistry / Q000166:cytology* / Q000648:ultrastructure; D010660:Phenylisopropyladenosine / Q000378:metabolism; D011869:Radioligand Assay; D011983:Receptors, Purinergic / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D014316:Tritium; D014665:Vasodilator Agents / Q000378:metabolism; D014970:Xanthines / Q000378:metabolism
chemical_list: D011983:Receptors, Purinergic; D014665:Vasodilator Agents; D014970:Xanthines; D014316:Tritium; D015762:2-Chloroadenosine; D010660:Phenylisopropyladenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); C051360:1,3-dipropyl-8-cyclopentylxanthine; D000241:Adenosine