Nucleoside transport in rat cerebral cortical synaptosomal membrane: a high affinity probe study.
1. The nucleoside transport system in rat cerebral cortical synaptosomes was investigated using [H3]p-nitrobenzylthioinosine (NBMPR) as a high affinity probe. 2. There are high affinity and low affinity binding sites for NBMPR on rat synaptosomal membranes. The high affinity sites showed a KD value of 0.05 nM and a Bmax value of 113 fmol/mg protein. 3. Biochemical characterization of the high affinity [H3]NBMPR binding sites indicated that they probably correspond to nucleoside transport sites. 4. Several known adenosine uptake inhibitors including clonazepam were tested for their interaction with this high affinity binding site. 5. The results suggest that hexobendine and papaverine inhibit adenosine uptake by occupying the [H3]NBMPR high affinity binding sites. 6. Clonazepam and dipyridamole appear to inhibit adenosine uptake in rat cerebral cortical synaptosomes via an interaction at a different site.
D000241:Adenosine / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D002540:Cerebral Cortex / Q000378:metabolism*; D007288:Inosine / Q000031:analogs & derivatives*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013570:Synaptic Membranes / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism; D013868:Thioinosine / Q000031:analogs & derivatives*
D013868:Thioinosine; D007288:Inosine; C001789:4-nitrobenzylthioinosine; D000241:Adenosine