Metabolism of extracellular adenine nucleotides by cultured rat brain astrocytes.
Intact astrocytes cultured from newborn rat cerebral cortex rapidly converted extracellular ATP to ADP. The ATPase responsible was apparently not saturated, even at 750 microM ATP. In contrast, the conversion of ADP to AMP was slow, and the reaction was limiting for the subsequent dephosphorylation process. Adenosine formation was the only fate for AMP. The reaction was catalyzed by 5'-nucleotidase with an apparent Km of 55 microM for AMP and appeared to be inhibited by high concentrations of ATP and ADP. Astrocytes were able to take up adenosine with an apparent Km value of 45 microM. Uptake was inhibited by dipyridamole but not by anti-5'-nucleotidase IgG. The results support the proposal that astrocytes play a role in modulating synaptic events involving ATP and adenosine.
Department of Biochemistry, Faculty of Medicine, University of Hong Kong.
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Lai
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Wong
D015720:5'-Nucleotidase / Q000378:metabolism; D000227:Adenine Nucleotides / Q000378:metabolism*; D000241:Adenosine / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001692:Biological Transport; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism*; D007288:Inosine / Q000378:metabolism; D007291:Inosine Monophosphate / Q000378:metabolism; D007700:Kinetics; D051381:Rats; D011919:Rats, Inbred Strains
D000227:Adenine Nucleotides; D007291:Inosine Monophosphate; D007288:Inosine; D000255:Adenosine Triphosphate; D015720:5'-Nucleotidase; D000241:Adenosine