Independent blood-brain barrier transport systems for nucleic acid precursors

Biochim Biophys Acta. 1975 Jun 25;394(2):211-9. doi: 10.1016/0005-2736(75)90259-x.


The blood-brain barrier permeability to certain 14-C-labelled purine and pyrimidine compounds was studied by simultaneous injection in conjunction with two reference isotopes into the rat common carotid artery and decapitation 15s later. The amount of 14-C-labelled base or nucleoside remaining in brain was expressed in relation to 3-H2O (a highly diffusible internal standard) and 113m-In-labelled EDTA (an essentially non-diffusible internal standard). Of the 17 compounds tested, measurable, saturable uptakes were established for adenine, adenosine, guanosine, inosine and uridine. Two independent transport systems in the rat blood-brain barrier were defined. One transported adenine (Km equals 0.027 mM) and could be inhibited with hypoxanthine. Adenosine (Km equals 0.018 mM), guanosine, inosine and uridine all cross-inhibit, defining a second independent nucleoside carrier system. Adenosine inhibited [14-D]uridine uptake more effectively than did uridine, suggesting a weaker affinity of uridine for this nucleoside carrier.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenine / metabolism
  • Adenosine / metabolism
  • Animals
  • Biological Transport, Active
  • Blood-Brain Barrier*
  • Brain / metabolism*
  • DNA / biosynthesis*
  • Guanosine / metabolism
  • Hypoxanthines / pharmacology
  • Inosine / metabolism
  • Kinetics
  • Purines / metabolism*
  • Pyrimidines / metabolism*
  • RNA / biosynthesis*
  • Rats
  • Uridine / metabolism


  • Hypoxanthines
  • Purines
  • Pyrimidines
  • Guanosine
  • Inosine
  • RNA
  • DNA
  • Adenine
  • Adenosine
  • Uridine