{"id":"68039c09-628a-5d6b-845f-791b2f587275","stable_key":"56f1d914-e7da-595a-af69-c217b2b47407:l-phenylalanine-brain-competition","predicate":"reduces","statement":"After 100 mg/kg oral phenylalanine in six healthy men, plasma phenylalanine rose about elevenfold and brain uptake of the artificial large-neutral-amino-acid tracer carbon-11 ACHC fell from 0.036 to 0.019 mL/g/min.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"negative","is_public":true,"mechanism_event_id":"5849301f-502a-538f-a8d1-c67add7d5f3a","mechanism_event_label":"A large phenylalanine load can compete with other molecules for brain entry.","subject":{"id":"190407ad-0219-54b5-b05f-7c75f3895ca6","slug":"l-phenylalanine","display_name":"L-Phenylalanine","entity_type_key":"small_molecule"},"object":{"id":"e0ece02d-1955-5661-b31a-83ffb8b7e461","slug":"human-achc-brain-influx","display_name":"Human brain influx of carbon-11 ACHC tracer","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"5849301f-502a-538f-a8d1-c67add7d5f3a","stable_key":"56f1d914-e7da-595a-af69-c217b2b47407:l-phenylalanine-brain-competition-event","event_type":"observed_relationship","label":"A large phenylalanine load can compete with other molecules for brain entry.","description":"After 100 mg/kg oral phenylalanine in six healthy men, plasma phenylalanine rose about elevenfold and brain uptake of the artificial large-neutral-amino-acid tracer carbon-11 ACHC fell from 0.036 to 0.019 mL/g/min.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"190407ad-0219-54b5-b05f-7c75f3895ca6","slug":"l-phenylalanine","display_name":"L-Phenylalanine","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"e0ece02d-1955-5661-b31a-83ffb8b7e461","slug":"human-achc-brain-influx","display_name":"Human brain influx of carbon-11 ACHC tracer","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"16d078ff-692c-50eb-a34b-c61ef43821e1","slug":"slc7a5","display_name":"Human L-type amino acid transporter 1 / LAT1 / SLC7A5","entity_type_key":"protein"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"availability_state","value_text":"biomarker_context","comparator":null,"unit":null,"notes":"Imported condition classification; unverified.","entity":null},{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human PET loading study in six men.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"ACHC is a transport tracer; each individual natural amino acid was not directly measured. This is not a normal-meal threshold.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"l-phenylalanine","display_name":"L-Phenylalanine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"A large phenylalanine load can compete with other molecules for brain entry.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Inhibition of neutral amino acid transport across the human blood-brain barrier by phenylalanine. · 1995 · https://pubmed.ncbi.nlm.nih.gov/7861158/ · DOI 10.1046/j.1471-4159.1995.64031252.x","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"trigger_kind","value_text":"biomarker_context","comparator":null,"unit":null,"notes":"Imported condition classification; unverified.","entity":null}],"evidence":[{"id":"555336a9-c80e-5ba8-a5c5-78af24171ce1","evidence_kind":"source_excerpt","locator":"Lines 190-196","start_line":190,"end_line":196,"excerpt":"## l-phenylalanine-brain-competition\nA large phenylalanine load can compete with other molecules for brain entry.\nAfter 100 mg/kg oral phenylalanine in six healthy men, plasma phenylalanine rose about elevenfold and brain uptake of the artificial large-neutral-amino-acid tracer carbon-11 ACHC fell from 0.036 to 0.019 mL/g/min.\nModel: Human PET loading study in six men.\nLimitations: ACHC is a transport tracer; each individual natural amino acid was not directly measured. This is not a normal-meal threshold.\nEvidence access: Primary abstract\nInhibition of neutral amino acid transport across the human blood-brain barrier by phenylalanine. · 1995 · https://pubmed.ncbi.nlm.nih.gov/7861158/ · DOI 10.1046/j.1471-4159.1995.64031252.x","model_system":"Human PET loading study in six men.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; evidence access and experimental limitations specified.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"54de7c56-1e60-5d7b-8ef9-852c58ae92ba","stable_key":"import-56f1d914-e7da-595a-af69-c217b2b47407","title":"L-Phenylalanine: transport, protein synthesis, cofactor recycling and cross-nutrient mechanisms (2026-09-19)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary references, access levels and experimental limitations individually identified. 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