| Project/Area Number |
14370016
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General physiology
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| Research Institution | Tokyo Medical University |
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Principal Investigator |
KONISHI Masato Tokyo Medical University, Medicine, Professor, 医学部, 教授 (20138746)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAYAMA Shinsuke Nagoya University, Department of Physiology, Associate Professor, 医学部, 助教授 (30192230)
MIYAZAKI Takefuimi Tokyo Medical University, Medicine, Assistant nufessor, 医学部, 講師 (60147212)
WATANABE Masaru Tokyo Medical University, Medicine, Assistant nufessor, 医学部, 講師 (60191798)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥9,300,000 (Direct Cost: ¥9,300,000)
Fiscal Year 2004: ¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 2003: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2002: ¥3,500,000 (Direct Cost: ¥3,500,000)
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| Keywords | intracellular Mg concentration / Mg transport / Mg-tolerant cells / fluorescent Mg indicator / Na-Mg exchange / molecular cloning / cardiac myocytes / functional analysis of membrane transprot / Mg輸送体 / 細胞内Mg / 交換輸送 / Na / 心筋 / Mg耐性 |
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| Research Abstract |
Mechanisms of Mg^<2+> extrusion from the cells were studied by measuring intracellular free concentrations of Mg^<2+> ([Mg^<2+>]_i) with the fluorescent indicator furaptra. We established a mutant strain of mouse renal cortical tubular (MCT) cells that could grow in culture media with very high Mg^<2+> concentrations ([Mg^<2+>]_o >100 mM : Mg-tolerant cells). The [Mg^<2+>]_i levels of the Mg-tolerant cells were kept lower than those in the wild-type cells. When [Mg^<2+>]_o was lowered from 51 mM to 1 mM, the extracellular Na-dependent decrease in [Mg^<2+>]_i was significantly faster in the Mg-tolerant cells, suggesting that Mg^<2+> extrusion by the Na^+-Mg^<2+> exchanger was enhanced in the Mg-tolerant cells. The DNA microarray analysis showed that expression of many genes were enhanced in the Mg-tolerant cells. Screening of these candidate genes for the Mg^<2+> transporter is now on-going.
In parallel with molecular cloning of the Mg^<2+> transporter, we also examined functional characteristics of the Na^+-Mg^<2+> exchange in cardiac myocytes. After Mg^<2+> loading of rat ventricular myocytes, Mg^<2+> efflux was induced by addition of extracellular Na^+, and the rates of decrease in [Mg^<2+>]_i were measured with furaptra, and were analyzed. A small elevation of [Mg^<2+>]_i significantly induced Mg^<2+> efflux with half maximal activation at 1.9 mM. On the other hand, extracellular Mg^<2+> inhibited the transport with 50% inhibition at 10 mM. The Mg^<2+> extrusion transport was accelerated by extracellular Na^+ with half maximal activation at 55 mM, and was slowed by intracellular Na^+ with 50% inhibition at 40 mM. Neither changes in intracellular and extracellular concentrations of Ca^<2+> nor extracellular K^+ concentration did not significantly influence the Mg^<2+> efflux rate. These results strongly support the Na^+-Mg^<2+> exchange hypothesis, and help detailed characterization of the transport.
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