title: L-methionine uptake by human cerebral cortex: maturation from infancy to old age.
abstract: Age-associated changes in amino acid transport from blood to normal frontal cortex were studied using positron emission tomography (PET). Seventeen patients, 1.8-71 yr, were injected intravenously with tracer doses of [11C] L-methionine and a baseline PET scan was obtained. To assess competitive inhibition of [11C]L-methionine uptake, patients received either oral L-phenylalanine or an i.v. infusion of amino acids 1 hr before a second PET study. Uptake of [11C]L-methionine by frontal cortex decreased seven-fold between 1.8 and 71 yr (r = -0.71; p less than 0.05). Blood-to-brain transfer of [11C]L-methionine, at 4.5 yr, exceeded mean adult values by more than five-fold. Competitive inhibition reduced L-methionine uptake in all patients older than 4.6 yr. These developmental changes parallel findings in animals. The neutral amino acid transport system may modulate human brain amino acid levels to meet changing developmental metabolic needs.
authors.affiliation: Department of Radiology, Johns Hopkins Hospital, Baltimore, Maryland.
authors.forename: L A
authors.initials: LA
authors.lastname: O'Tuama
authors.forename: P C
authors.initials: PC
authors.lastname: Phillips
authors.forename: Q R
authors.initials: QR
authors.lastname: Smith
authors.forename: Y
authors.initials: Y
authors.lastname: Uno
authors.forename: R F
authors.initials: RF
authors.lastname: Dannals
authors.forename: A A
authors.initials: AA
authors.lastname: Wilson
authors.forename: H T
authors.initials: HT
authors.lastname: Ravert
authors.forename: S
authors.initials: S
authors.lastname: Loats
authors.forename: H A
authors.initials: HA
authors.lastname: Loats
authors.forename: H N
authors.initials: HN
authors.lastname: Wagner
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D001921:Brain / Q000254:growth & development; D001932:Brain Neoplasms / Q000000981:diagnostic imaging; D002250:Carbon Radioisotopes; D002540:Cerebral Cortex / Q000000981:diagnostic imaging* / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D008715:Methionine / Q000378:metabolism; D014055:Tomography, Emission-Computed
chemical_list: D002250:Carbon Radioisotopes; D008715:Methionine