[3H]adenosine binding sites on 108CC15 neuroblastoma × glioma hybrid cell line and rat brain membranes

Adenosine binding sites on 108CC15 neuroblastoma x glioma hybrid cells and rat brain membranes were investigated using [(3)H]adenosine as labelled ligand. Both the hybrid cells and brain membranes were found to have a high affinity binding site, K(d) 0.8 and 3 nM respectively. The same ligand was used to demonstrate two lower affinity binding sites on brain membranes, K(d)s 1.4 and 29.1 ?M and a single low affinity site on the hybrid cells, K(d) 2.6 ?M. Structure activity studies of the low affinity binding site on hybrid cells showed this to be an 'R' adenosine receptor of the A(2) subtype. It is concluded that [(3)H]adenosine can be used to demonstrate both high and low affinity binding sites and that 108CC15 hybrid cells provide a valuable system for studying adenosine receptors.