1990 Fiscal Year Final Research Report Summary
Cystine/Glutamate Exchange Transport System in Brain
| Project/Area Number |
01570122
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
General medical chemistry
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| Research Institution | University of Tsukuba |
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Principal Investigator |
BANNAI Shiro Univ. of Tsukuba, Inst. Basic Med. Sci., Prof., 基礎医学系, 教授 (70019579)
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| Co-Investigator(Kenkyū-buntansha) |
ISHII Tetsuro Univ. of Tsukuba, Inst. Basic Med. Sci., Assist. Prof., 基礎医学系, 講師 (20111370)
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| Project Period (FY) |
1989 – 1990
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| Keywords | Cystine / Glutamic acid / Amino acid transport / Neuron / Astrocyte / Glutathione |
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| Research Abstract |
The uptake of glutamate in rat glioma C-6 cells and cultured astrocytes derived from newborn rat cerebral hemispheres was found to be mediated by glutamate/aspartate system (System X^-_) and cystine/glutamate exchange system (System x^-_). In C-6 cells the glutamate uptake via System X^-_ and x^-_ approximately accounted for 35% and 55% of the total uptake, respectively, at 0.05 mM glutamate. In cultured astrocytes the glutamate uptake via System X^-_ was very potent, whereas the uptake vis System x^-_ was relatively weak and its contribution to the total uptake of glutamate seemed almost negligible. However, in both C-6 cells and astrocytes System x^-_ was necessary for the uptake of cystine. Cystine in the culture medium was an essential precursor of glutathione and the inhibition of the cystine uptake via System x^-_ led to a severe deficiency in glutathione. Brain cells prepared from fetal rat (16 days gestation) showed a System x^-_ activity. These cells differentiated to neuron-like cells and astrocyte-like cells when cultured. Astrocyte-like cells showed a high activity of System x^-_ whereas neuron-like cells showed a very low activity. A glutathione level of neuron-like cells was maintained when they were co-cultured with astrocyte-like cells, but the level went down when they were separated from astrocyte-like cells. It was suggested that astrocytes took up cystine via System x^-_ and reduced it to cysteine, which was released from the cells and utilized by neurons to maintain their glutathione level.
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