title: Neutral amino acid uptake by the isolated perfused sheep choroid plexus.
abstract: 1. The uptake of neutral amino acids from the blood into the cells of the choroid plexus was studied by means of the rapid (less than 40 s) single-circulation paired-tracer dilution technique in the isolated perfused choroid plexus of the sheep. 2. The study provides the first direct evidence for the carrier-mediated entry of neutral amino acids from blood into the cells of the choroid plexus. 3. In the terms of Christensen's classification the presence of L-amino acid carrier systems for large neutral amino acids with bulky side chains has been demonstrated. 4. No measurable uptake of [14C]methyl amino isobutyric acid ([14C]MeAIB) during a single passage through the choroid plexus circulation was demonstrated which indicates the probable absence of a significant 'A' transport system. 5. The uptake of small neutral amino acids such as glycine and L-alanine was shown to be carrier-mediated. Results suggest that these amino acids are mainly transported by the glycine and ASC carrier systems, respectively. 6. The results suggest that there is a similarity between the transport systems for neutral amino acids on the blood side of both the blood-brain barrier and blood-cerebrospinal fluid barrier, the exception being for the presence of a glycine carrier on the blood side of the choroid plexus.
authors.affiliation: Sherrington School of Physiology, United Medical School of Guy's Hospitals, London.
authors.forename: J E
authors.initials: JE
authors.lastname: Preston
authors.forename: M B
authors.initials: MB
authors.lastname: Segal
authors.forename: G J
authors.initials: GJ
authors.lastname: Walley
authors.forename: B V
authors.initials: BV
authors.lastname: Zlokovic
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000621:Aminoisobutyric Acids / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D001692:Biological Transport; D002555:Cerebrospinal Fluid / Q000502:physiology; D002831:Choroid Plexus / Q000378:metabolism*; D005260:Female; D005998:Glycine / Q000378:metabolism; D066298:In Vitro Techniques; D007930:Leucine / Q000378:metabolism; D008297:Male; D008353:Mannitol / Q000378:metabolism; D010649:Phenylalanine / Q000378:metabolism; D012756:Sheep
chemical_list: D000596:Amino Acids; D000621:Aminoisobutyric Acids; C017911:2-(methylamino)isobutyric acid; D008353:Mannitol; D010649:Phenylalanine; D007930:Leucine; D005998:Glycine