Specific [3H]-guanosine binding sites in rat brain membranes
Article first published online: 2 FEB 2009
2002 British Pharmacological Society
British Journal of Pharmacology
Volume 135, Issue 4, pages 969–976, February 2002
How to Cite
Traversa, U., Bombi, G., Iorio, P. D., Ciccarelli, R., Werstiuk, E. S. and Rathbone, M. P. (2002), Specific [3H]-guanosine binding sites in rat brain membranes. British Journal of Pharmacology, 135: 969–976. doi: 10.1038/sj.bjp.0704542
- Issue published online: 2 FEB 2009
- Article first published online: 2 FEB 2009
- (Received August 7, 2001, Revised November 27, 2001, Accepted November 30, 2001)
- rat brain membranes;
- purine analogues;
- guanosine binding sites
Extracellular guanosine has diverse effects on many cellular components of the central nervous system, some of which may be related to its uptake into cells and others to its ability to release adenine-based purines from cells. Yet other effects of extracellular guanosine are compatible with an action on G-protein linked cell membrane receptors.
Specific binding sites for [3H]-guanosine were detected on membrane preparations from rat brain. The kinetics of [3H]-guanosine binding to membranes was described by rate constants of association and dissociation of 2.6122×107 M−1 min−1 and 1.69 min−1, respectively.
A single high affinity binding site for [3H]-guanosine with a KD of 95.4±11.9 nM and Bmax of 0.57±0.03 pmol mg−1 protein was shown.
This site was specific for guanosine, and the order of potency in displacing 50 nM [3H]-guanosine was: guanosine=6-thio-guanosine>inosine>6-thio-guanine>guanine. Other naturally occurring purines, such as adenosine, hypoxanthine, xanthine caffeine, theophylline, GDP, GMP and ATP were unable to significantly displace the radiolabelled guanosine. Thus, this binding site is distinct from the well-characterized receptors for adenosine and purines.
The addition of GTP produced a small concentration-dependent decrease in guanosine binding, suggesting this guanosine binding site was linked to a G-protein.
Our results therefore are consistent with the existence of a novel cell membrane receptor site, specific for guanosine.
British Journal of Pharmacology (2002) 135, 969–976; doi:10.1038/sj.bjp.0704542