Extracellular Interconversion of Nucleotides Reveals an Ecto-Adenylate Kinase Activity in the Rat Hippocampus |
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Authors: | Beáta Sperlágh E Sylvester Vizi |
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Institution: | (1) Department of Pharmacology, Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony u. 43, Budapest, 1083, Hungary |
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Abstract: | Here, the extracellular interconversion of nucleotides and nucleosides was investigated in rat hippocampal slices and synaptosomes
by an HPLC-UV technique. Adenosine 5′-triphosphate (ATP) was converted to adenosine 5′-diphosphate (ADP), adenosine 5′-monophosphate
(AMP), adenosine, inosine, and hypoxanthine in the slices, whereas ADP elicited parallel and concentration-dependent formation
of ATP and AMP. The specific adenylate kinase inhibitor diadenosine pentaphosphate decreased the rate of decomposition of
ADP and inhibited the formation of ATP. No substantial changes in the interconversion of ADP to ATP and AMP were found in
the presence of dipyridamole, flufenamic acid, the P2 receptor antagonist pyridoxal-5-phosphate-6-azophenyl-2′,4′-disulphonic
acid tetrasodium (PPADS), and the alkaline phosphatase substrate para-nitrophenylphosphate. Negligible levels of nucleotides were generated when uridine 5′-diphosphate (UDP), AMP or adenosine
were used as substrates. Ecto-adenylate kinase activity was also observed in purified synaptosomes. In summary, we demonstrate
the presence of an ecto-adenylate kinase activity in the hippocampus, which is a previously unrecognized pathway that influences
the availability of purines in the central nervous system. |
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Keywords: | ADP ATP Hippocampus Ecto-adenylate kinase Diadenosine pentaphosphate NTPDase |
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