Effects of Ca^<2+> and Epinephrine on Ca^<2+> Recirculation Fraction and Total Ca^<2+> Handling in Canine Left Ventricles

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Author(s)

Abstract

We investigated the effects of intracoronary Ca<SUP>2+</SUP> and epinephrine on the intracellular Ca<SUP>2+</SUP> recirculation fraction (RF) and total Ca<SUP>2+</SUP> handling in the left ventricle (LV) of the excised cross-circulated canine heart preparation. We analyzed LV postextrasystolic potentiation (PESP) following a spontaneous extrasystole that occurred sporadically under constant atrial pacing. All PESPs decayed in alternans and none decayed monotonically. We extracted an exponential decay component from the alternans PESP, determined its beat constant (τ<SUB>e</SUB>), and calculated RF=exp(−1/τ<SUB>e</SUB>). Increased intracoronary Ca<SUP>2+</SUP> slightly increased τ<SUB>e</SUB> and RF, but epinephrine did not change them, although both agents enhanced LV contractility 2-3 times. Neither Ca<SUP>2+</SUP> nor epinephrine affected the sinusoidal decay of the alternans PESP. These results indicate that RF via the sarcoplasmic reticulum was slightly augmented by Ca<SUP>2+</SUP>, but not by epinephrine. We combined these RF data with LV Ca<SUP>2+</SUP> handling O<SUB>2</SUB> consumption data and obtained 40-110 μmol/kg as the total amount of Ca<SUP>2+</SUP> handled in one cardiac cycle in the control and enhanced contractile states. These results indicate that this new LV-level approach seems to better the understanding of the Ca<SUP>2+</SUP> mass dynamics responsible for the mechanoenergetics enhanced by inotropic interventions.

Journal

  • The Japanese Journal of Physiology

    The Japanese Journal of Physiology 48(2), 123-132, 1998-04

    THE PHYSIOLOGICAL SOCIETY OF JAPAN

References:  36

Cited by:  1

Codes

  • NII Article ID (NAID)
    10008304285
  • NII NACSIS-CAT ID (NCID)
    AA00691224
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    0021521X
  • NDL Article ID
    4514079
  • 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  CJPref  NDL  J-STAGE 
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