[(3)H]8-Ethyl-4-methyl-2-phenyl-(8R)-4,5,7,8-tetrahydro-1H-imidazo[2,1-i]-purin-5-one ([(3)H]PSB-11), a novel high-affinity antagonist radioligand for human A(3) adenosine receptors

Bioorg Med Chem Lett. 2002 Feb 11;12(3):501-3. doi: 10.1016/s0960-894x(01)00785-5.


This study describes the preparation and binding properties of [(3)H]PSB-11, a novel, potent, and selective antagonist radioligand for human A(3) adenosine receptors (ARs). [(3)H]PSB-11 binding to membranes of Chinese hamster ovary (CHO) cells expressing the human A(3) AR was saturable and reversible. Saturation experiments showed that [(3)H]PSB-11 labeled a single class of binding sites with high affinity (K(D)=4.9 nM) and limited capacity (B(max)=3500 fmol/mg of protein). PSB-11 is highly selective versus the other adenosine receptor subtypes. The new radioligand shows an extraordinarily low degree of non-specific binding rendering it a very useful tool for studying the (patho)physiological roles of A(3 )ARs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • Catalysis
  • Cricetinae
  • Humans
  • Hydrogenation
  • Imidazoles / chemical synthesis
  • Imidazoles / pharmacology*
  • Kinetics
  • Membranes / metabolism
  • Purinergic P1 Receptor Antagonists*
  • Purines / chemical synthesis
  • Purines / pharmacology*
  • Radiopharmaceuticals / chemical synthesis
  • Radiopharmaceuticals / pharmacology*
  • Receptor, Adenosine A3


  • 8-ethyl-4-methyl-2-phenyl-4,5,7,8-tetrahydro-1H-imidazo(2,1-i)purin-5-one
  • Imidazoles
  • Purinergic P1 Receptor Antagonists
  • Purines
  • Radiopharmaceuticals
  • Receptor, Adenosine A3