title: Alanine metabolism, transport, and cycling in the brain.
abstract: Brain glutamate/glutamine cycling is incomplete without return of ammonia to glial cells. Previous studies suggest that alanine is an important carrier for ammonia transfer. In this study, we investigated alanine transport and metabolism in Guinea pig brain cortical tissue slices and prisms, in primary cultures of neurons and astrocytes, and in synaptosomes. Alanine uptake into astrocytes was largely mediated by system L isoform LAT2, whereas alanine uptake into neurons was mediated by Na(+)-dependent transporters with properties similar to system B(0) isoform B(0)AT2. To investigate the role of alanine transport in metabolism, its uptake was inhibited in cortical tissue slices under depolarizing conditions using the system L transport inhibitors 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid and cycloleucine (1-aminocyclopentanecarboxylic acid; cLeu). The results indicated that alanine cycling occurs subsequent to glutamate/glutamine cycling and that a significant proportion of cycling occurs via amino acid transport system L. Our results show that system L isoform LAT2 is critical for alanine uptake into astrocytes. However, alanine does not provide any significant carbon for energy or neurotransmitter metabolism under the conditions studied.
authors.affiliation: School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Stefan
authors.initials: S
authors.lastname: Bröer
authors.affiliation: School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Angelika
authors.initials: A
authors.lastname: Bröer
authors.affiliation: School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Jonas T
authors.initials: JT
authors.lastname: Hansen
authors.affiliation: School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: William A
authors.initials: WA
authors.lastname: Bubb
authors.affiliation: School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Vladimir J
authors.initials: VJ
authors.lastname: Balcar
authors.affiliation: School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Fatima A
authors.initials: FA
authors.lastname: Nasrallah
authors.affiliation: School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Brett
authors.initials: B
authors.lastname: Garner
authors.affiliation: School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Caroline
authors.initials: C
authors.lastname: Rae
mesh_terms: D000409:Alanine / Q000378:metabolism*; D027182:Amino Acid Transport System y+ / Q000037:antagonists & inhibitors / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry / Q000187:drug effects / Q000502:physiology*; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002478:Cells, Cultured; D004734:Energy Metabolism / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D027301:Fusion Regulatory Protein 1, Light Chains; D018698:Glutamic Acid / Q000378:metabolism*; D006168:Guinea Pigs; D051379:Mice; D018377:Neurotransmitter Agents / Q000096:biosynthesis; D009865:Oocytes; D009924:Organ Culture Techniques; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D009435:Synaptic Transmission / Q000502:physiology; D013574:Synaptosomes
chemical_list: D027182:Amino Acid Transport System y+; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D027301:Fusion Regulatory Protein 1, Light Chains; D018377:Neurotransmitter Agents; C518286:SLC7A8 protein, mouse; D018698:Glutamic Acid; D000641:Ammonia; D000409:Alanine