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VITAMIN B 6 TRANSPORT IN THE CENTRAL NERVOUS SYSTEM: IN VITRO STUDIES
Author(s) -
Spector Reynold
Publication year - 1978
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.1471-4159.1978.tb10798.x
Subject(s) - choroid plexus , choroid , cerebrospinal fluid , in vitro , central nervous system , intracellular , chemistry , biology , biochemistry , endocrinology , retina , neuroscience
— The transport into and release of tritium labeled vitamin B 6 ([ 3 H]B 6 ) from rabbit brain slices and isolated choroid plexuses were studied. In vitro , both brain slices and choroid plexus concentrated [ 3 H]B 6 by an energy dependent uptake system when [ 3 H]pyridoxine (PIN) was added to the incubation medium. Most of the [ 3 H] within the tissues was phosphorylated [ 3 H]B 6 . In each tissue, the nonphosphorylated vitamers inhibited the uptake of [ 3 H]PIN from the medium significantly more than the phosphorylated vitamers. The concentrations of the nonphosphorylated B 6 vitamers necessary to inhibit brain and choroid plexus uptake of [ 3 H]PIN from the medium by 50% were approx 0.4 μ m and 5–10 μ m respectively after a 30 min incubation. Both brain slices and choroid plexus readily released (46 and 56% respectively in 30 min) previously accumulated [ 3 H]B 6 into artificial CSF. However, brain slices released only nonphosphorylated [ 3 H]B 6 , whereas the choroid plexus released predominantly phosphorylated [ 3 H]B 6 . Addition of unlabeled PIN to the release media significantly increased the percentage of [ 3 H]B 6 released by both brain slices and choroid plexus. The results of these in vitro studies provide evidence that: (1) both brain slices and chloroid plexus possess specific uptake and release mechanisms for B 6 , and (2) these mechanisms tend to regulate intracellular B 6 levels. These studies also suggest that the choroid plexus serves as a locus for the transfer of B 6 from blood to CSF and is the source of most of the phosphorylated B 6 in CSF.