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


Our laboratory has recently cloned and expressed a brain- and neuron- specific Na+-dependent inorganic phosphate (P(i)) cotransporter that is constitutively expressed in neurons of the rat cerebral cortex, hippocampus, and cerebellum. We have now characterized Na+-dependent 32P(i) cotransport in cultured fetal rat cortical neurons, where >90% of saturable P(i) uptake is Na+-dependent. Saturable, Na+-dependent 32P(i) uptake was first observed in primary cultures of cortical neurons at 7 days in vitro (DIV) and was maximal at 12 DIV. Na+dependent P(i) transport was optimal at physiological temperature (37°C) and pH (7.0-7.5), with apparent K(m) values for P(i) and Na+ of 54 ± 12.7 μM and 35 ± 4.2 mM, respectively. A reduction in extracellular Ca2+ markedly reduced (>60%) Na+-dependent P(i) uptake, with a threshold for maximal P(i) 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 32P(i) cotransported with Na+ was concentrated in the adenine nucleotides. Inhibitors of oxidative metabolism, such as rotenone, oligomycin, or dinitrophenol, dramatically decreased Na+-dependent P(i) import rates. These data establish the presence of a Na+-dependent P(i) cotransport system in neurons of the CNS, demonstrate the Ca2-dependent nature of 32P(i) uptake, and suggest that the neuronal Na+-dependent P(i) cotransporter may import P(i) 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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