Characterization of Na+‐Dependent Phosphate Uptake in Cultured Fetal Rat Cortical Neurons

Michele Glinn, Binhui Ni, Steven M. Paul

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21 Scopus citations


Abstract: Our laboratory has recently cloned and expressed a brain‐ and neuron‐specific Na+‐dependent inorganic phosphate (Pi) cotransporter that is constitutively expressed in neurons of the rat cerebral cortex, hippocampus, and cerebellum. We have now characterized Na+‐dependent 32Pi cotransport in cultured fetal rat cortical neurons, where >90% of saturable Pi uptake is Na+‐dependent. Saturable, Na+‐dependent 32Pi uptake was first observed in primary cultures of cortical neurons at 7 days in vitro (DIV) and was maximal at 12 DIV. Na+‐dependent Pi transport was optimal at physiological temperature (37°C) and pH (7.0–7.5), with apparent Km values for Pi and Na+ of 54 ± 12.7 µM and 35 ± 4.2 mM, respectively. A reduction in extracellular Ca2+ markedly reduced (>60%) Na+‐dependent Pi uptake, with a threshold for maximal Pi import of 1–2.5 mM CaCl2. Primary cultures of fetal cortical neurons incubated in medium where equimolar concentrations of choline were substituted for Na+ had lower levels of ATP and ADP and higher levels of AMP than did those incubated in the presence of Na+. Furthermore, a substantial fraction of the 32Pi cotransported with Na+ was concentrated in the adenine nucleotides. Inhibitors of oxidative metabolism, such as rotenone, oligomycin, or dinitrophenol, dramatically decreased Na+‐dependent Pi import rates. These data establish the presence of a Na+‐dependent Pi cotransport system in neurons of the CNS, demonstrate the Ca2+‐dependent nature of 32Pi uptake, and suggest that the neuronal Na+‐dependent Pi cotransporter may import Pi required for the production of high‐energy compounds vital to neuronal metabolism.

Original languageEnglish
Pages (from-to)2358-2365
Number of pages8
JournalJournal of Neurochemistry
Issue number5
StatePublished - Nov 1995


  • ATP biosynthesis
  • Calcium transport
  • Cortical neurons
  • Extracellular calcium
  • Na‐dependent phosphate transport
  • Neuronal metabolism


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