Properties of Spontaneous Electrical Activity in Smooth Muscle of the Guinea-Pig Renal Pelvis

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Author(s)

Abstract

In the guinea-pig renal pelvis, most smooth muscle cells examined (>90%), using a conventional microelectrode, had a resting membrane potential of about −50 mV and produced spontaneous action potentials with initial fast spikes and following plateau potentials. The remainder (<10%) had a resting membrane potential of about −40 mV and produced periodical depolarization with slow rising and falling phases. Experiments were carried out to investigate the properties of spontaneous action potentials. The potentials were abolished by nifedipine, suggesting a possible contribution of voltage-gated Ca<sup>2+</sup> channels to the generation of these potentials. Niflumic acid and 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS), inhibitors of Ca<sup>2+</sup>-activated Cl<sup>−</sup> channels, showed different effects on the spontaneous action potentials, and the former but not the latter inhibited the activities, raised the question of an involvement of Cl<sup>−</sup> channels in the generation of these activities. Depleting internal Ca<sup>2+</sup> stores directly with caffeine or indirectly by inhibiting Ca<sup>2+</sup>-ATPase at the internal membrane with cyclopiazonic acid (CPA) prevented the generation of spontaneous activity. Chelating intracellular Ca<sup>2+</sup> by 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) increased the amplitude of the spike component of spontaneous activity. Indomethacin inhibited the spontaneous activity, whereas prostaglandin F<sub>2α</sub> enhanced it. The results indicate that in smooth muscle of the renal pelvis, the generation of spontaneous activity is causally related to the activation of voltage-gated Ca<sup>2+</sup> channels through which the influx of Ca<sup>2+</sup> may trigger the release of Ca<sup>2+</sup> from the internal stores to activate a set of ion channels at the membrane. Endogenous prostaglandins may be involved in the initiation of spontaneous activity.<br>

Journal

  • The Japanese Journal of Physiology

    The Japanese Journal of Physiology 50(6), 597-603, 2000-12-01

    THE PHYSIOLOGICAL SOCIETY OF JAPAN

References:  28

Codes

  • NII Article ID (NAID)
    10008292432
  • NII NACSIS-CAT ID (NCID)
    AA00691224
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    0021521X
  • NDL Article ID
    5706324
  • NDL Source Classification
    ZS8(科学技術--医学--解剖学・生理学・生化学)
  • NDL Call No.
    Z53-D40
  • Data Source
    CJP  NDL  J-STAGE 
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