The binding of [3H]adenosine to synaptosomal and other preparations from the mammalian brain.
1. A high-affinity adenosine-binding site with Kd(adenosine) 0.5-1.3 microM was demonstrated in particulate and synaptosomal fractions isolated from the cerebral cortex of guinea pig, rat and ox. 2. Binding of [3H]adenosine to this site was inhibited by theophylline and by 2-chloroadenosine, but not by four other adenosine analogues. 3. Endogenous adenosine, found to be present in some preparations at approx. 1 pmol/mg of protein, diminished the binding capacity of the preparations for [3H]adenosine. 4. Addition of the adenosine deaminase inhibitor erythro-9-[1-(1-hydroxyethyl)heptyl]-adenine revealed the presence of a second lower affinity binding site with Kd (adenosine) 5-9 microM and a higher maximal adenosine-binding capacity. The inhibitor partially blocked binding to the high-affinity site in preparations from which adenosine deaminase had been removed by washing. 5. To preparations of particulate fractions maintained under iso-osmotic conditions, adenosine attachment was non-saturable and temperature-dependent, indicating the existence of an active uptake process. 6. The location and binding constant of the high-affinity adenosine-binding site suggest that it corresponds to the receptor site for adenosine-activated adenylate cyclase.
D000241:Adenosine / Q000378:metabolism*; D058892:Adenosine Deaminase Inhibitors; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002540:Cerebral Cortex / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008928:Mitochondria / Q000378:metabolism; D051381:Rats; D013347:Subcellular Fractions / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*
D058892:Adenosine Deaminase Inhibitors; D000241:Adenosine