| Project/Area Number |
12470151
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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 |
Circulatory organs internal medicine
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| Research Institution | Hamamatsu University School of Medicine (2001-2002)
Nagoya University (2000) |
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Principal Investigator |
HAYASHI Hideharu Hamamatsu University School of Medicine, Department of Medicine, Professor, 医学部, 教授 (50135258)
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| Co-Investigator(Kenkyū-buntansha) |
KATOH Hideki Hamamatsu University School of Medicine, Department of Medicine, Assistant, 医学部, 助手 (80314029)
本荘 晴朗 名古屋大学, 環境医学研究所, 助教授 (70262912)
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| Project Period (FY) |
2000 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥10,200,000 (Direct Cost: ¥10,200,000)
Fiscal Year 2002: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2001: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2000: ¥8,200,000 (Direct Cost: ¥8,200,000)
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| Keywords | diazaoxide / laser scanning confocal microscopy / mitochondrial membrane potential (Δφ_m) / Ca^<2+> transient / Ca^<2+> spark / mPTP / cyclospoin A / 5-hydroxydecanoic acid / Ca^<2+> transient / Ca^<2+> Spark / Cyclosporin A / Diazoxide / ミトコンドリア / ミトコンドリア内Ca^<2+>濃度 / Saponin / permeability transition pore / 細胞保護効果 / cyclosporin A / 筋小細体 |
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| Research Abstract |
Mitochondrial K_<ATP> channel (mitoK_<ATP>) has been implicated as end effectors and/or triggers of ischemic preconditioning (IP). Although a mitoK_<ATP> opener, diazoxide, mimics IP, the mechanisms for the cardioprotective action remain unclear. We measured Ca^<2+> transients (CaT) and mitochondrial inner membrane potential (Δφ_m) with confocal microscopy and fluorescent probes, fluo-4 and tetramethylrhodamine ethyl ester perchlorate (TMRE), in rat ventricular myocytes. Diazoxide increased the amplitudes and diastolic levels of CaT dose-dependently. The effects of diazoxide on CaT were inhibited by the mitoK_<ATP> antagonist, sodium 5-hydroxydecanoic acid (5-HD ; 100μmol/L) whereas the application of diazoxide caused little change in Δφ_m. After SR function was disabled with ryanodine and thapsigargin, the effects of diazoxide on CaT were still observed. The opening of the mitochondrial permeability transition pore (mPTP) was monitored with fluorescent calcein. Diazoxide accelerated the leakage of calcein from mitochondrial matrix (16 % of control, P<0.05), and this effect was inhibited by cyclosporin A (CsA ; 2 μmol/L). CsA also abolished the effect of diazoxide on CaT. Diazoxide oxidized flavoprotein fluorescence reversibly and this effect was partially blunted by CsA (by 24%, P<0.05). We conclude that in rat ventricular myocytes, diazoxide modulates the opening of mPTP, resulting in the increase in CaT, independently of the changes in Δφ_m. The action of diazoxide on mPTP also affects mitochondrial redox state.
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