Norepinephrine : and K^+ : Induced Mn^<2+> : Dependent Contractions and the Dynamics of Intracellular Mn^<2+> Changes in Dispersed Smooth Muscle Cells From Ca^<2+> : Depleted Mn^<2+> : Loaded Vas Deferens of the Guinea Pig

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Abstract

The cellular mechanisms of norepinephrine (NE)-induced Mn<SUP>2+</SUP>-dependent contractions were investigated in dispersed smooth muscle cells from guinea pig vas deferens by characterizing the effects of NE and K<SUP>+</SUP> on cell length observed by videotape microscopy and on intracellular Mn<SUP>2+</SUP> and Ca<SUP>2+</SUP> concentration ([Mn<SUP>2+</SUP>]<SUB>i</SUB> and [Ca<SUP>2+</SUP>]<SUB>i</SUB>) observed by confocal microscopy. Both stimulants induced slow sustained contraction in Ca<SUP>2+</SUP>-depleted, Mn<SUP>2+</SUP>-accumulated cells (Mn<SUP>2+</SUP>-loaded cells), whereas they induced biphasic contractions in normal cells that were neither Ca<SUP>2+</SUP>-depleted nor Mn<SUP>2+</SUP>-loaded. In both conditions, the number of cells responding to NE as well as the magnitude of NE-induced contractions increased in a dose-dependent manner. Contractions induced by K<SUP>+</SUP> in Mn<SUP>2+</SUP>-loaded strip preparations were markedly smaller than those induced by NE. Although individual K<SUP>+</SUP>-induced contractions in responsive Mn<SUP>2+</SUP>-loaded cells were as large as those induced by NE, a much smaller percentage of Mn<SUP>2+</SUP>-loaded cells was responsive to K<SUP>+</SUP> than to NE. These results are consistent with the idea that the contractions of strip preparations may reflect the magnitude of the contractions of individual cells as well as the percentage of responsive cells in the preparations. Inconsistent with the contractions, the [Mn<SUP>2+</SUP>]<SUB>i</SUB> rise induced by K<SUP>+</SUP> was larger than that induced by NE, and the percentage of cells responsive to K<SUP>+</SUP> was larger than that responsive to NE. These results suggest that NE may increase the Mn<SUP>2+</SUP> sensitivity of contractile elements.

Journal

  • The Japanese Journal of Pharmacology

    The Japanese Journal of Pharmacology 78(3), 323-329, 1998-11-01

    The Japanese Pharmacological Society

References:  19

Codes

  • NII Article ID (NAID)
    10008681256
  • NII NACSIS-CAT ID (NCID)
    AA00691188
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    00215198
  • NDL Article ID
    4610821
  • NDL Source Classification
    ZS51(科学技術--薬学)
  • NDL Call No.
    Z53-D199
  • Data Source
    CJP  NDL  J-STAGE 
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