Evaluation of radioiodinated 8-cyclopentyl-3-[(E)-3-iodoprop-2-en-1-YL]-1-propylxanthine ([* I]CPIPX) as a new potential A1 adenosine receptor antagonist for SPECT

8-Cyclopentyl-3-[(E)-3-[I-131]iodoprop-2-en-1-yl]-1-propylxanthine (2*) was generated by iododestannylation of the tributyl-stannyl-precursor with [I-131]NaI and chloramine T. The radiochemical yield of 2* was 82 +/- 4%, and the purity exceeded 98%. The specific activity was 33 +/- 19 GBq/mumol. Affinities for rat, pig and human A, adenosine receptors (A(1)ARs) were in the low nanomolar range, but poor selectivity for the human A(1)AR over the A(2A)AR was found. Additionally, in vitro and ex vivo autoradiographic studies revealed high unspecific binding which makes this ligand unsuitable for SPELT imaging. (C) 2003 Elsevier Inc. All rights reserved