Nucleoside transport in rat cerebral cortical synaptosomal membrane: a high affinity probe study

Area of Science:

• Neuroscience
• Pharmacology
• Biochemistry

Background:

• The nucleoside transport system is crucial for brain function.
• Understanding adenosine uptake mechanisms is vital for neurological research.

Purpose of the Study:

• To characterize the nucleoside transport system in rat cerebral cortical synaptosomes.
• To identify binding sites for nucleoside transport inhibitors.

Main Methods:

• Utilized [H3]p-nitrobenzylthioinosine ([H3]NBMPR) as a high-affinity probe.
• Investigated binding kinetics (KD, Bmax) of [H3]NBMPR.
• Assessed the inhibitory effects of various compounds on adenosine uptake.

Main Results:

• Identified high-affinity ([H3]NBMPR) binding sites (KD=0.05 nM, Bmax=113 fmol/mg protein) on synaptosomal membranes.
• Biochemical characterization suggests these sites correspond to nucleoside transporters.
• Hexobendine and papaverine inhibit adenosine uptake by binding to high-affinity [H3]NBMPR sites.
• Clonazepam and dipyridamole inhibit adenosine uptake through a different mechanism.

Conclusions:

• Rat cerebral cortical synaptosomes possess distinct high-affinity nucleoside binding sites.
• Hexobendine and papaverine are identified as inhibitors acting at these specific sites.
• Clonazepam and dipyridamole exhibit differential inhibition mechanisms for adenosine uptake.