Pharmaceutical Research

, Volume 21, Issue 9, pp 1680–1685 | Cite as

Role of PEPT2 in the Choroid Plexus Uptake of Glycylsarcosine and 5-Aminolevulinic Acid: Studies in Wild-Type and Null Mice

  • Scott M. Ocheltree
  • Hong Shen
  • Yongjun Hu
  • Jianming Xiang
  • Richard F. Keep
  • David E. Smith

Abstract

Purpose. To determine the importance of PEPT2 in the uptake of glycylsarcosine (GlySar) and 5-aminolevulinic acid (5-ALA) in mouse choroid plexus whole tissue.

Methods. Uptake studies were performed in bicarbonate artificial cerebrospinal fluid buffer using choroid plexuses isolated from PEPT2+/+ and PEPT2-/- mice. [14C]GlySar and [14C]5-ALA were studied as a function of temperature, concentration, potential inhibitors, and low sodium conditions.

Results. PEPT2-/- mice exhibited a 90% reduction in GlySar uptake (p < 0.001) and a 92% reduction in 5-ALA uptake (p < 0.001) as compared to wild type animals. At 4°C (vs. 37°C), GlySar uptake was reduced by 95% in PEPT2+/+ mice; no difference was observed in null animals. Unlabeled GlySar inhibited the uptake of [14C]GlySar in PEPT2+/+ mice (p < 0.01); self-inhibition did not occur in PEPT2-/- mice. GlySar demonstrated saturable uptake in PEPT2+/+ mice (Vmax = 16.4 pmol mg−1 min−1, Km = 70 μM, Kd = 0.014 μl mg−1 min−1), however, uptake was linear in PEPT2-/- mice (Kd = 0.023 μl mg−1 min−1). Low sodium buffer (1 mM) resulted in 75% and 59% reductions, respectively, in GlySar (p < 0.001) and 5-ALA (p < 0.01) uptake in PEPT2+/+ mice; no differences were observed in PEPT2-/- mice. Overall, about 90-95% of the choroid plexus uptake of GlySar and 5-ALA was mediated by PEPT2, with about 5-10% of the residual uptake occurring by nonspecific mechanisms.

Conclusions. The results demonstrate that PEPT2 is the only transporter responsible for the choroid plexus uptake of GlySar and 5-ALA. They also suggest a role for PEPT2 in the clearance of dipeptides and endogenous peptidomimetics from cerebrospinal fluid.

5-ALA choroid plexus GlySar knockout mouse PEPT2 

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Copyright information

© Springer Science+Business Media, Inc. 2004

Authors and Affiliations

  • Scott M. Ocheltree
    • 1
  • Hong Shen
    • 1
  • Yongjun Hu
    • 1
  • Jianming Xiang
    • 2
  • Richard F. Keep
    • 2
  • David E. Smith
    • 1
  1. 1.Department of Pharmaceutical SciencesThe University of MichiganAnn ArborUSA
  2. 2.Departments of Neurosurgery and PhysiologyThe University of MichiganAnn ArborUSA

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