The Role of Blood-Brain Barrier Transport of Tryptophan and Other Neutral Amino Acids in the Regulation of Substrate-Limited Pathways of Brain Amino Acid Metabolism
- 1 January 1979
- book chapter
- review article
- Published by Springer Science and Business Media LLC
- No. 15,p. 43-54
- https://doi.org/10.1007/978-3-7091-2243-3_4
Abstract
Many pathways of essential neutral amino acid metabolism in the CNS are influenced by precursor availability. Since the delivery of circulating amino acids to brain cells is primarily controlled by the rate of amino acid transport through the blood-brain barrier (BBB), pathways of brain amino acid metabolism are ultimately influenced by the activity (Km, Vmax) of the BBB neutral amino acid transport system. The Km of BBB transport is in the 0.1–0.6 mM range, which approximates the physiologic plasma levels and forms the basis of the unusual sensitivity of the brain to competition effects on neutral amino acid transport. Unlike the brain, the Km of amino acid transport into other organs is in the 1–10 mM range or greater, which frees these tissues from competition effects in the physiologic range of plasma amino acids. Tryptophan circulates 80–90% bound to albumin; however, the capacity/affinity ratio of the BBB neutral amino acid transport system exceeds the capacity/affinity ratio of albumin binding of tryptophan, which enables the carrier to strip tryptophan off albumin as it traverses the brain capillary. The activity of the BBB neutral amino acid transport system is probably not modulated by insulin, but is influenced by changes in thyroid hormone status; the transport system is also induced in states of hepatic encephalopathy and this induction process is the primary cause of the increased brain tryptophan and serotonin levels in cirrhosis.Keywords
This publication has 33 references indexed in Scilit:
- INCREASE IN LARGE NEUTRAL AMINO ACID TRANSPORT INTO BRAIN BY INSULINJournal of Neurochemistry, 1978
- FUNCTIONAL HOMOGENEITY OF LEUCINE POOL IN RETINA CELLS1Journal of Neurochemistry, 1976
- THE EFFECT OF DIETARY HISTIDINE LEVEL ON THE CARNOSINE CONCENTRATION OF RAT OLFACTORY BULBSJournal of Neurochemistry, 1976
- DO CHANGES IN BLOOD LEVELS OF OTHER AROMATIC AMINOACIDS INFLUENCE LEVODOPA THERAPY?The Lancet, 1976
- TRANSCRIPTION OF REPEATED AND UNIQUE DNA SEQUENCES IN BRAIN NUCLEIJournal of Neurochemistry, 1976
- SYNTHETIC AMINO ACIDS AND THE NATURE OF l‐DOPA TRANSPORT AT THE BLOOD‐BRAIN BARRIERJournal of Neurochemistry, 1975
- HYPOTHYROIDISM AND AMINOACID ENTRY INTO BRAIN AND MUSCLEThe Lancet, 1975
- Kinetic analysis of blood-brain barrier transport of amino acidsBiochimica et Biophysica Acta (BBA) - Biomembranes, 1975
- L-dopa level in plasma, primary condition for the kinetic effectJournal of Neural Transmission, 1973
- The influx of amino acids into the brain of the rat in vivo : the essential compared with some non-essential amino acidsProceedings of the Royal Society of London. B. Biological Sciences, 1973