| Project/Area Number |
11670049
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | Iwate Medical University |
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Principal Investigator |
KUBOKAWA Manabu Iwate Medical University, Physiology II, Professor, 医学部, 教授 (70153327)
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| Co-Investigator(Kenkyū-buntansha) |
HIRANO Junko Iwate Medical University, Physiology II, Assistant, 医学部, 助手 (40316352)
NAKAMURA Kazuyoshi Iwate Medical University, Physiology II, Assistant, 医学部, 助手 (50237385)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2000: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1999: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Keywords | kidney / proximal tubule / membrane potential / K^+ channel / ATP / phosphorylation / dephosphorylation / cell pH / 膜電位 / K^+channel / 細胞内Ca^<2+> / リン酸化酵素 |
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| Research Abstract |
Renal potassium channels along the nephron play a key role in formation of membrane potential, which serves as driving forces for rheogenic ion transport across the tubular epithelia. In this study, we investigated the regulatory mechanisms of K^+ channels in opossum and human renal proximal tubule cells by using the patch-clamp technique. In opossum kidney cells, inwardly rectifying K^+ channels with inward conductance of about 90pS were most frequently observed in cell-attached patches under the control condition. We found out that activity of this K^+ channel was enhanced by protein kinase A (PKA) and inhibited by protein phosphatase types 1 and 2A (PP-1 and PP-2A). These results suggest that PKA-mediated phosphorylation is dephosphorylated at least in part by PP-1 and PP-2A in this channel.
On the other hand, previous reports showed that ATP effects on inwardly rectifying K^+ channels in proximal tubule cells varied in individual animal species. Namely, one is the ATP-sensitive (inh
… More
ibitable) channel and the other is the ATP-dependent channel. However, little is known about K^+ channels in human proximal tubule cells. Thus in the next step, we applied the patch-clamp technique to the human proximal tubule cells of normal kidney origin. We identified an inwardly rectifying K^+ channels with an inward conductance of about 42pS in the surface membrane of the proximal tubule cells. This K^+ channel was the most dominant K^+ channel in cell-attached patches, and ATP was required to maintain channel activity in inside-out patches. The ATP effect on channel activity was dose-dependently stimulatory. Thus the inwardly rectifying K^+ channel in the human proximal tubule cells was not ATP-sensitive channel. Moreover, we found that channel activity was enhanced by PKA, and significantly affected by internal pH.In addition to this channel, we characterized a large conductance K^+ channel, which is activated by Ca^<2+> and inhibited by ATP.Our data suggest that the human proximal tubule cells are useful for investigation of regulatory mechanisms and physiological functions of ion channels. Less
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