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DISTINCT PATTERNS OF ENTRY OF TWO NONMETABOLIZABLE AMINO ACIDS INTO BRAIN AND OTHER ORGANS OF INFANT GUINEA PIGS 1, 2
Author(s) -
Schain R. J.,
Watanabe Kathy S.
Publication year - 1972
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.1471-4159.1972.tb01281.x
Subject(s) - in vivo , kidney , biology , mammalian brain , guinea pig , medicine , amino acid , distribution (mathematics) , endocrinology , chemistry , biochemistry , neuroscience , mathematical analysis , microbiology and biotechnology , mathematics
— Entry of [3‐ 14 C] α‐aminoisobutyric acid (AIB) and [1‐ 14 C] 1‐aminocyclopentanecarboxylic acid (cycloleucine) into the brain and other organs of the infant guinea pig has been investigated in vivo. The entry of [ 14 C]AIB into brain was markedly restricted in comparison to its entry into other organs. The mean distribution ratio ( 14 C in tissue water/ 14 C in plasma water) achieved in brain at 45 min after administration of a pulse of [ 14 C]AIB was 0.3. All other organs studied concentrated [ 14 C]AIB from the blood stream, with the greatest uptake occurring in liver and kidney, in which distribution ratios reached values of 5–10. In contrast to AIB, [ 14 C]cycloleucine entered the brain at a rate approximately the same as that into other organs. Distribution ratios for [ 14 C]cycloleucine ranged between 0.5 and 2.0 for all organs. During the first few days of postnatal life, there was a sharp increase of concentrative uptake of [ 14 C]AIB into liver and kidney. The entry of [ 14 C]AIB into brain remained unchanged during this period. There was a small (35 percent) decrease in the rate of entry of [ 14 C]cycloleucine into brain during the first 3 days of postnatal life. Since [ 14 C]AIB is known to be concentrated from the surrounding medium by brain slices in vitro, we concluded that the locus of restriction of the entry of [ 14 C]AIB into the brain in vivo is at the blood‐brain barrier. We hypothesize that this property of the barrier is important in preventing concentrative uptake of pharmacologically active and potentially harmful amino acids by brain tissue.