title: Characterization of human and rodent native and recombinant adenosine A(2B) receptors by radioligand binding studies.
abstract: Adenosine A(2B) receptors of native human and rodent cell lines were investigated using [(3)H]PSB-298 [(8-{4-[2-(2-hydroxyethylamino)-2-oxoethoxy]phenyl}-1-propylxanthine] in radioligand binding studies. [(3)H]PSB-298 showed saturable and reversible binding. It exhibited a K(D) value of 60 +/- 1 nM and limited capacity (B(max) = 3.511 fmol per milligram protein) at recombinant human adenosine A(2B) receptors expressed in human embryonic kidney cells (HEK-293). The addition of sodium chloride (100 mM) led to a threefold increase in the number of binding sites recognized by the radioligand. The curve of the agonist 5'-N-ethylcarboxamidoadenosine (NECA) was shifted to the right in the presence of NaCl, while the curve of the antagonist PSB-298 was shifted to the left, indicating that PSB-298 may be an inverse agonist at A(2B) receptors. Adenosine A(2B) receptors were shown to be the major adenosine A(2) receptor subtype on the mouse neuroblastoma x rat glioma hybrid cell line NG108-15 cells. Binding studies at rat INS-1 cells (insulin secreting cell line) demonstrated that [(3)H]PSB-298 is a selective radioligand for adenosine A(2B) binding sites in this cell line.
authors.affiliation: Pharmaceutical Institute, Pharmaceutical Sciences Bonn (PSB), Pharmaceutical Chemistry Poppelsdorf, University of Bonn, Bonn, Germany.
authors.forename: Daniela C G
authors.initials: DC
authors.lastname: Bertarelli
authors.forename: Martina
authors.initials: M
authors.lastname: Diekmann
authors.forename: Alaa M
authors.initials: AM
authors.lastname: Hayallah
authors.forename: Dorothee
authors.initials: D
authors.lastname: Rüsing
authors.forename: Jamshed
authors.initials: J
authors.lastname: Iqbal
authors.forename: Birgit
authors.initials: B
authors.lastname: Preiss
authors.forename: Eugen J
authors.initials: EJ
authors.lastname: Verspohl
authors.forename: Christa E
authors.initials: CE
authors.lastname: Müller