Role of PEPT2 in the Choroid Plexus Uptake of Glycylsarcosine and 5-Aminolevulinic Acid: Studies in Wild-Type and Null Mice Article DOI:
Cite this article as: Ocheltree, S.M., Shen, H., Hu, Y. et al. Pharm Res (2004) 21: 1680. doi:10.1023/B:PHAM.0000041465.89254.05 Abstract . To determine the importance of PEPT2 in the uptake of glycylsarcosine (GlySar) and 5-aminolevulinic acid (5-ALA) in mouse choroid plexus whole tissue. Purpose . Uptake studies were performed in bicarbonate artificial cerebrospinal fluid buffer using choroid plexuses isolated from PEPT2 Methods +/+ and PEPT2 -/- mice. [ 14C]GlySar and [ 14C]5-ALA were studied as a function of temperature, concentration, potential inhibitors, and low sodium conditions. . PEPT2 Results -/- 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 (V max = 16.4 pmol mg −1 min −1, K m = 70 μM, K d = 0.014 μl mg −1 min −1), however, uptake was linear in PEPT2 -/- mice (K d = 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. . 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. Conclusions 5-ALA choroid plexus GlySar knockout mouse PEPT2 REFERENCES
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