Solubilization and partial characterization of adenosine binding sites from rat brainstem.

Binding sites for adenosine were solubilized from rat brainstem membranes with either sodium cholate, sodium deoxycholate or 3-[(3-cholamidopropyl)dimethyl-ammonio]-1-propanesulfonate. About 30% of the binding activity were released by [3H]phenylisopropyladenosine (PIA) binding. Specific [3H]PIA binding to the solubilized fraction was saturable and was found to be a monophasic saturation profile. In contrast, [3H]PIA binding to the brainstem membranes exhibited a biphasic profile suggesting the presence of two binding sites. By gel filtration on a Sepharose CL-6B column, the adenosine binding site--detergent complex was estimated to have app. Mr 280000 and rs = 5.4 nm.