Metabolism of Extracellular Adenine Nucleotides by Cultured Rat Brain Astrocytes

Abstract

: Intact astrocytes cultured from newborn rat cerebral cortex rapidly converted extracellular ATP to ADP. The ATPase responsible was apparently not saturated, even at 750 μM 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 S'‐nucleotidase with an apparent K_m of 55 μM for AMP and appeared to be inhibited by high concentrations of ATP and ADP.Astrocytes were able to take up adenosine with an apparent K_m value of 45 μM. 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.