title: Cerebrospinal and plasma amino acid concentrations after administration of i.v. glycyl-glutamine and glycyl-tyrosine containing amino acid solutions in humans.
abstract: BACKGROUND
  Glycyl-glutamine and glycyl-tyrosine may supply adequate glutamine and tyrosine in amino acid solutions for parenteral nutrition. However, plasma peptides may be transported into the cerebrospinal fluid, exerting effects on the neuronal tissue. Cerebrospinal fluid (CSF) and plasma amino acid concentrations after administration of a glycyl-glutamine/glycyltyrosine supplemented amino acid solution were therefore evaluated in a randomized controlled comparison with a conventional amino acid infusion.
  
  
  METHODS
  Dipeptide/amino acid solutions (0.60 mL/h/kg; 82.2 mg total dipeptides/amino acids/h/kg) or conventional amino acid solutions (0.73 mL/h/kg; 83.2 mg total amino acids/h/kg) were infused in 15 patients per group scheduled to undergo spinal anesthesia for urologic surgery over a 12-hour period preoperatively. Plasma amino acids were measured before the infusion was started. CSF and venous concentrations were analyzed simultaneously before the infusion was stopped. CSF samples were drawn through the spinal needle for anesthesia.
  
  
  RESULTS
  The dipeptide-containing solution did not increase either dipeptide to detectable levels in the CSF (detection limit < 5.0 nmol/mL). Venous glycyl-glutamine increased from below detection limits up to 308 +/- 111 nmol/mL (p < .05), whereas glycyl-tyrosine could not be found. In the dipeptide group, venous glutamine and tyrosine were higher (p < .05) but only tyrosine appeared in small amounts (p < .05) in the cerebrospinal fluid.
  
  
  CONCLUSIONS
  This study provides no evidence to support a CSF entry of IV glycyl-tyrosine and glycyl-glutamine under conditions of a normal blood-brain barrier in the adult (detection limit 5 nmol/mL). The data suggest that amino acid solutions containing these dipeptides may be used in parenteral solutions for nutrition support.
authors.affiliation: University Clinic of Anesthesiology, University Clinics of Ulm, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Himmelseher
authors.forename: E
authors.initials: E
authors.lastname: Pfenninger
authors.forename: P
authors.initials: P
authors.lastname: Herrmann
mesh_terms: D000368:Aged; D000596:Amino Acids / Q000008:administration & dosage / Q000097:blood* / Q000134:cerebrospinal fluid*; D001692:Biological Transport; D004151:Dipeptides / Q000008:administration & dosage / Q000378:metabolism*; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care
chemical_list: D000596:Amino Acids; D004151:Dipeptides; C046223:N-glycylglutamic acid; C022013:glycyltyrosine