1987 Fiscal Year Final Research Report Summary
A study on ion transport systems in heart muscle
| Project/Area Number |
61570438
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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 |
Circulatory organs internal medicine
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| Research Institution | National Cardiovascular Center |
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Principal Investigator |
SHIGEKAWA Munekazu National Cardiovascular Center, 循環分子生理部, 部長 (00113738)
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| Co-Investigator(Kenkyū-buntansha) |
渡辺 公英 国立循環器病センター研究所, 循環分子生理部, 室長 (00093485)
OGURUSU Taro National Cardiovascular Center, 病因部, 室員 (70177202)
WAKABAYASHI Shigeo National Cardiovascular Center, 病因部, 室員 (70158583)
WATANABE Takahide National Cardiovascular Center
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| Project Period (FY) |
1986 – 1987
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| Keywords | Na^+ / H^+ exchanger / Na pump / 心筋小胞体Caポンプ |
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| Research Abstract |
In this project we have studled propertles of some of the membrane transport systems for Ca^<2+>,Na^+ and H^+ which regulates contraction of heart muscle. Following are the results obtained.
1.Na^+/H^+ exchange activity in cardiac sarcolemma:We We characterised the pH gradient-dependent Na^+ transport or Na^+ gradient-dependent H^+ transport activities measured in sarcolemma vesicles lsolated from bovine cardiac muscle. Treatment of sarcolemma vesicles with ATP-<gamma>-s in the presence of um Ca^<2+> increased both^<22>Na uptake and H^+ transport activities,suggesting that protein phosphorylation by endogenous kinase(s)may be involved in regulation of Na^+/H^+ exchange activity.We have also devised a procedure by which the Na^+/H^+ exchange activity can be reconstituted into artiflcial liposomes using cholate and freeze-thaw sonication method.
2.Purification of Na pump from heart muscle:A procedure was devised for preparation of highly active(Na,K)ATPase from rat heart which had a specific actibity of 200-600 umo/mg/hr.The procedure is simple and can be applied to small amounts of heart muscle(-1g).The ATPase activity was more than 90% sensitive to 1 mM ouabain.The ouabain sensitivity is biphasic with about 20% of the activity being inhibited at 10 uM ouabain.
3.Reaction mechanism for the Ca pump of cardlac sarcoplasmic reticulum(sr): GTP-supported Ca transport by canine cardiac SR was studied in detail because others reported that it is not coupled to GTP hydrolysis catalized by the Ca pump and that it does not occur via phosphoenzyme intermediates(EP).We found that GTP-supported Ca transport and GTP hydrolysis behaved similarly under various conditions.We presented evidence that EP does occur as an intermediate for GTP hydrolysis althogh enzyme phosphorylation by GTP is very slow as compared with ATP.
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Research Products
(12 results)
