Satoko Ohkubo1, Junko Kimura2 and Isao Matsuoka2,*
1Department of Cellular Signaling, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan
2Department of Pharmacology, School of Medicine, Fukushima Medical University, Fukushima 960-1295, Japan
Abstract: We previously demonstrated that extracellular adenine nucleotides induced cyclic AMP elevation in NG108-15 cells. This response was resistant to adenosine deaminase (ADA) and the ecto-5ó-nucleotidase (CD73) inhibitor a,b-methylene ADP (a,b-MeADP), but was inhibited by both P1- and P2-receptor antagonists. In the present study, we investigated the relationship between adenine nucleotide-induced cyclic AMP elevation and extracellular adenosine formation. ATP, AMP and b,g-methylene ATP (b,g-MeATP) were time-dependently metabolized to adenosine in NG108-15 cells. Adenosine formations from ATP, AMP and b,g-MeATP were not affected by a,b-MeADP, but suppressed by the P2-receptor antagonist pyridoxalphosphate-6-azophenyl-2ó,4ó-disulphonic acid (PPADS). A close correlation between extracellular adenosine formation and cyclic AMP increasing effects were obtained with several adenine nucleotide agonists in NG108-15 cells as well as their parent cell line C6Bu-1 and N18TG-2 cells, all of which possess functional adenosine╩A2 receptors. When NG108-15 cells were incubated with [3H]ATP or [3H]AMP in the presence of ADA, [3H]adenosine was found to distribute dominantly on the cell surface. NG108-15 cells expressed mRNA for the ecto-ATPase and nucleotide pyrophosphatase, but not for CD73. These results suggest that local adenosine formation by an ecto-enzyme distinct from CD73 is involved in adenine nucleotide-induced cyclic AMP formation in NG108-15 cells.
Keywords: Extracellular adenine nucleotide metabolism, Ecto-nucleotide pyrophosphatase,
Ecto-5ó-nucleotidase, Adenosine A2A receptor, NG108-15 cell
Copyrightę The Japanese Pharmacological Society 2000
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