title: PEPT2-mediated uptake of neuropeptides in rat choroid plexus.
abstract: OBJECTIVE
  The peptide transporter PEPT2 was recently shown to be functionally active in rat choroid plexus, suggesting that it may play a role in neuropeptide homeostasis in the cerebrospinal fluid. This study, therefore, examined the role of PEPT2 in mediating neuropeptide uptake into choroid plexus.
  
  
  METHODS
  Whole-tissue rat choroid plexus uptake studies were performed on GlySar in the absence and presence of neuropeptides and on carnosine.
  
  
  RESULTS
  The neuropeptides NAAG, CysGly, GlyGln, kyotorphin, and carnosine inhibited the uptake of radiolabeled GlySar at 1.0 mM concentrations. In contrast, TRH, [D-Arg2]-kyotorphin, glutathione, and homocarnosine did not inhibit GlySar uptake. Kyotorphin, an analgesic, was a competitive inhibitor of GlySar with a Ki of 8.0 microM. The direct uptake of carnosine was also shown to be mediated by PEPT2 in isolated choroid plexus (Km = 39.3 microM; Vmax = 73.9 pmol/mg/min). Radiolabeled carnosine uptake was inhibited by 1.0 mM concentrations of GlySar or carnosine but not homocarnosine, L-histidine, or beta-alanine.
  
  
  CONCLUSIONS
  These findings indicate that PEPT2 mediates the uptake of a diverse group of neuropeptides in choroid plexus, and suggests a role for PEPT2 in the regulation of neuropeptides, peptide fragments, and peptidomimetics in cerebrospinal fluid.
authors.affiliation: College of Pharmacy and Upjohn Center for Clinical Pharmacology, The University of Michigan, Ann Arbor 48109, USA.
authors.forename: N S
authors.initials: NS
authors.lastname: Teuscher
authors.forename: R F
authors.initials: RF
authors.lastname: Keep
authors.forename: D E
authors.initials: DE
authors.lastname: Smith
mesh_terms: D000818:Animals; D002336:Carnosine / Q000493:pharmacokinetics; D002831:Choroid Plexus / Q000378:metabolism*; D004151:Dipeptides / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D008297:Male; D009479:Neuropeptides / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000493:pharmacokinetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D027981:Symporters / Q000502:physiology*
chemical_list: D004151:Dipeptides; D009479:Neuropeptides; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2; C004194:glycylsarcosine; D002336:Carnosine