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Activation of Ionic Channels during Regulatory Volume Decrease

Research Project

Project/Area Number 60480109
Research Category

Grant-in-Aid for General Scientific Research (B)

Allocation TypeSingle-year Grants
Research Field General physiology
Research InstitutionKyoto University

Principal Investigator

OKADA Yasunobu  Kyoto University, Faculty of Medicine, 医学部, 講師 (10025661)

Project Period (FY) 1985 – 1986
Project Status Completed (Fiscal Year 1986)
Budget Amount *help
¥6,500,000 (Direct Cost: ¥6,500,000)
Fiscal Year 1986: ¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1985: ¥4,000,000 (Direct Cost: ¥4,000,000)
KeywordsCell Volume Regulation / <K^+> channel / <Cl^-> channel / Cytosolic <Ca^(2+)> concentration / 小腸上皮細胞
Research Abstract

During exposure to a hypotonic bathing solution, cultured epithelial cells (Intestine 407) exhibited initial osmotic swelling and a subsequent regulatory volume decrease (RVD). Intracellular recordings showed that the RVD was associated with biphasic hyperpolarizations under a control ionic condition (4.2 mM <K^+> , 60 mM <Cl^-> ). The hyperpolarizations were blocked by the application of quinine, an inhibitor of <Ca^(2+)> - activated <K^+> channels. In a low <Cl^-> solution (4.2 mM <K^+> , 6 mM <Cl^-> ), the osmotic challenge provoked a characteristic biphasic response; that is, a transient, quinine-sensitive hyperpolarization was followed by a prolonged depolarization. The depolarization was blocked by SITS, a blocker of <Cl^-> channels, but not by quinine. Two-microelectrode voltage clamp studies indicated that biphasic membrane currents consisting of a <K^+> current and a <Cl^-> current were associated with the membrane potential changes upon the RVD process. To determine which current is activated by intracellular <Ca^(2+)> ions, studies by intracellular <Ca^(2+)> injections and with <Ca^(2+)> -selective microelectrodes were carried out. Electrophoretic microinjection of <Ca^(2+)> ions into the cell evoked a transient monophasic hyperpolarization, which was sensitive to quinine (not SITS), but never induced a subsequent depolarization in a low <Cl^-> solution. Intracellular <Ca^(2+)> measurements during the RVD process under a low <Cl^-> condition demonstrated that a sizable increase in the cytosolic free <Ca^(2+)> concentration was associated with an initial hyperpolarization ( <K^+> current activation) but not with a subsequent depolarization ( <Cl^-> current activation). Based on these observations, it is concluded that separate electroconductive pathways, <K^+> and <Cl^-> channels, are operating during the RVD process in Intestine 407 cells, and that the former is activated by increased cytoplasmic free <Ca^(2+)> ions but the latter is not.

Report

(1 results)
  • 1986 Final Research Report Summary
  • Research Products

    (6 results)

All Other

All Publications (6 results)

  • [Publications] A.Hazama: Cell Structure and Function. 10. 513 (1985)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1986 Final Research Report Summary
  • [Publications] A.Hazama: Journal of Physiological Society of Japan. 48. 161 (1986)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1986 Final Research Report Summary
  • [Publications] A.Hazama: Cell Structure and Function. 11. 515 (1986)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1986 Final Research Report Summary
  • [Publications] A. Hazama: "Independent activation of <K^+> and <Cl^-> channels during a regulatory volume decrease of cultured epithlial cells." Cell structure and Function. 10. 513 (1985)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1986 Final Research Report Summary
  • [Publications] A. Hazama: "Activation of <K^+> and <Cl^-> channels and changes in the intracellular ion concentrations during cell volume regulation in hypotonic solutions." Journal of Physiological Society of Japan. 48. 161 (1986)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1986 Final Research Report Summary
  • [Publications] A. Hazama: "Regulatory volume decrease is coupled to significant changes in the intracellular concentrations of <K^+> , <Cl^-> and <Na^+> ." Cell Structure and Function. 11. 515 (1986)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1986 Final Research Report Summary

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Published: 1987-03-31   Modified: 2016-04-21  

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