| Project/Area Number |
63570420
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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 Cardiovasc. Ctr, Dept.of molec. physiol, head, 循環分子生理部, 部長 (00113738)
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| Co-Investigator(Kenkyū-buntansha) |
IWATA Yuko 国立循環器病センター研究所, 循環分子生理部, 室員 (80171908)
FURUKAWA Ken-ichi National Cardiovasc. Ctr, Dept.of molec. physiol, Research associate, 循環分子生理部, 室員 (20165468)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1989: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1988: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | Vascular Smooth Muscle / Ca^<2+> pump / protein kinase C / calcium / membrane potential / cyclic nucleotide / 膜電位 / 細胞膜CaATPポンプ / 環状ヌクレオチド / 細胞内Caイオン濃度 / プロテインキナーゼ / フォルボールエステル / 心房性利尿ペプチド / ニトロプルシド |
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| Research Abstract |
We have devised a method by which we estimated quantitativelv activities of the sarcolemmal Ca pump and NalCa exchanger in intact cultured rat aotic smooth muscle cells. Using this method, we examined the effect of the activation of various protein kinases on activity of sarcolemmal Ca pump. We found that the Ca pump activity was stimulated by agents, which increased the intracellular cGMP level, and TPA, an activator of protein kinase C (PKC), whereas it was not affected by the cAMP-producing agents. We then examined the biochemical basis for the stimulatory effect of PKC. We found that PKC treatment resulted in phosphorylation of the Ca-ATPase to a level of about 1 mol per mol of the enzyme. Since there was good parallelity between the ATPase phosphorylation and the extent of enzyme activation, we concluded that the sarcolemmal Ca pump is regulated through its direct phosphorylation. In the next series of experiments, in which we used the same experimental system, we examined the effect of membrane potential (E_m) on the activity of the sarcolemmal Ca pump. Inside-negative K diffusion potential higher or lower than the resting E_m was artificially imposed with various concentrations of extracellular K and valinomycin. We found that the Ca pump was accelerated by depolarizing E_m, whereas it was retarded by hyperpolarizing E_m. These results therefore strongly suggested that the Ca pump is electrogenic and that alteration in E_m can modulate the intracellular Ca concentration in intact smooth muscle cells by changing the rate of Ca extrusion by the Ca pump. In the third series of experiments, we tested the effect of a rise in the intracellular cAMP concentration on the ATP-induced Ca mobilization in cultured aotic smooth muscle cells. We found that cAMP potentiated the ATP-induced intracellular Ca transient and that this vas due to the enhancement of IP_3-induced Ca release from the intracellular Ca store.
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