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Kinetics of Neutral Amino Acid Transport Through the Blood‐Brain Barrier of the Newborn Rabbit
Author(s) -
Pardridge William M.,
Mietus Lawrence J.
Publication year - 1982
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1982.tb05335.x
Subject(s) - amino acid , glutamine , blood–brain barrier , tryptophan , kinetics , alanine , biochemistry , albumin , chemistry , biology , endocrinology , central nervous system , physics , quantum mechanics
Abstract: Since protein synthesis in the developing brain may, under certain conditions, be limited by amino acid availability, the present studies were undertaken to characterize the kinetics of large neutral amino acid transport through the blood‐brain barrier (BBB) of the newborn rabbit. The K m , V max , and K D of the transport of eight amino acids were determined by a nonlinear regression analysis of data obtained with the carotid injection technique. Compared with kinetic parameters observed for the adult rat, the K m , V max , and K D of amino acid transport were all two‐ to threefold higher in the newborn. Albumin was found to bind tryptophan actively in vitro , but had no inhibitory effect on tryptophan transport through the newborn BBB. Glutamine was transported through the BBB of the newborn at rates severalfold higher than are seen in the adult rat. However, glutamine transport was not inhibited by high concentrations of N ‐methylaminoisobutyric acid (NMAIB), a model amino acid that is specific for the alanine‐preferring or A‐system present in peripheral tissues. In conclusion, these studies show that the BBB neutral amino acid transport system of the newborn rabbit has a lower affinity and higher capacity than does the BBB of the adult rat. Under conditions of high plasma amino acids, the increased capacity of the newborn transport system allows for a higher rate of amino acid transport into brain than would occur via the lower capacity system present in the adult rat brain.