Characterization of adenosine binding sites in bovine testicular tissue using 8-cyclopentyl-1,3-[ 3H]dipropylxanthine

The existence of specific adenosine binding sites in bovine testicular tissue was evaluated using the novel antagonist radioligand 8-cyclopentyl-1,3-[ 3H]dipropylxanthine ([ 3H]DPCPX). Saturation analysis revealed specific binding that was saturable at ∼ 1 nM. Scatchard analysis indicated a single class of binding sites with K D = 0.26 nM and a B max = 0.37 pmol/mg protein. Affinity profiles suggest an A 1 subtype recognition site that is different from the classical A 1 adenosine receptor. The results presented should prove useful in subsequent studies concerning heterogeneity among adenosine receptors and also aid in discerning the role of adenosine in reproduction.