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
*Corresponding author.ﾊﾊFAX:+81-24-548-0575
E-mail: isom@fmu.ac.jp
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-5｢-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-2｢,4｢-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ﾊ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-5｢-nucleotidase, Adenosine A2A
receptor, NG108-15 cell
Copyrightｩ The Japanese Pharmacological Society 2000
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