Ca^<2+> Spark as a Regulator of Ion Channel Activity

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Author(s)

    • OHYA Susumu
    • Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Nagoya City University
    • MURAKI Katsuhiko
    • Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Nagoya City University
    • WATANABE Minoru
    • Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Nagoya City University

Abstract

Ca<SUP>2+</SUP> spark is a local and transient Ca<SUP>2+</SUP> release from sarcoplasmic reticulum (SR) through the ryanodine receptor Ca<SUP>2+</SUP>-releasing channel (RyR). In cardiac myocytes, Ca<SUP>2+</SUP> spark is an elementary unit of Ca<SUP>2+</SUP>-induced Ca<SUP>2+</SUP> release (CICR) by opening of RyR(s) in junctional SR (jSR), which is triggered by Ca<SUP>2+</SUP>-influx through L-type Ca<SUP>2+</SUP> channels to the narrow space between a transverse tubule and jSR. Ca<SUP>2+</SUP> spark has, therefore, been described as the evidence for “the local control of excitation-contraction coupling”. In contrast, Ca<SUP>2+</SUP> sparks in smooth muscle have been reported in relation to Ca<SUP>2+</SUP>-dependent K<SUP>+</SUP> (K<SUB>Ca</SUB>) channel activation and muscle relaxation. A spontaneous Ca<SUP>2+</SUP> spark in a superficial area activates 10 - 100 K<SUB>Ca</SUB> channels nearby and induces membrane hyperpolarization, which reduces Ca<SUP>2+</SUP> channel activity. In several types of smooth muscle cells, which have relatively high membrane excitability, an action potential (AP) elicits 5 - 20 Ca<SUP>2+</SUP> hot spots (evoked sparks with long life) in the early stage via CICR in discrete superficial SR elements and activates K<SUB>Ca</SUB>-channel current highly responsible for AP repolarization and afterhyperpolarization. CICR available for contraction may occur more slowly by the propagation of CICR from superficial SR to deeper ones. The regulatory mechanism of ion channel activity on plasma membrane by superficial SR via Ca<SUP>2+</SUP> spark generation in smooth muscle cells may be analogously common in several types of cells including neurons.

Journal

  • The Japanese Journal of Pharmacology

    The Japanese Journal of Pharmacology 80(1), 1-8, 1999-05-01

    The Japanese Pharmacological Society

References:  42

Cited by:  6

Codes

  • NII Article ID (NAID)
    10008194375
  • NII NACSIS-CAT ID (NCID)
    AA00691188
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    00215198
  • NDL Article ID
    4732957
  • NDL Source Classification
    ZS51(科学技術--薬学)
  • NDL Call No.
    Z53-D199
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
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