Mechanoenergetics Characterizing Oxygen Wasting Effect of Caffeine in Canine Left Ventricle

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Author(s)

Abstract

Caffeine causes a considerable O<sub>2</sub> waste for positive inotropism in myocardium by complex pharmacological mechanisms. However, no quantitative study has yet characterized the mechanoenergetics of caffeine, particularly its O<sub>2</sub> cost of contractility in the E<sub>max</sub>-PVA-VO<sub>2</sub> framework. Here, E<sub>max</sub> is an index of ventricular contractility, PVA is a measure of total mechanical energy generated by ventricular contraction, and VO<sub>2</sub> is O<sub>2</sub> consumption of ventricular contraction. The E<sub>max</sub>-PVA-VO<sub>2</sub> framework proved to be powerful in cardiac mechanoenergetics. We therefore studied the effects of intracoronary caffeine at concentrations lower than 1 mmol/l on left ventricular (LV) E<sub>max</sub> and VO<sub>2</sub> for excitation-contraction (E-C) coupling in the excised cross-circulated canine heart. We enhanced LV E<sub>max</sub> by intracoronary infusion of caffeine after β-blockade with propranolol and compared this effect with that of calcium. We obtained the relation between LV VO<sub>2</sub> and PVA with E<sub>max</sub> as a parameter. We then calculated the VO<sub>2</sub> for the E-C coupling by subtracting VO<sub>2</sub> under KCl arrest from the PVA-independent (or zero-PVA) VO<sub>2</sub> and the O<sub>2</sub> cost of E<sub>max</sub> as the slope of the E-C coupling VO<sub>2</sub>-E<sub>max</sub> relation. We found that this cost was 40% greater on average for caffeine than for calcium. This result, for the first time, characterized integratively cardiac mechanoenergetics of the O<sub>2</sub> wasting effect of the complex inotropic mechanisms of intracoronary caffeine at concentrations lower than 1 mmol/l in a beating whole heart.<br>

Journal

  • The Japanese Journal of Physiology

    The Japanese Journal of Physiology 50(2), 257-265, 2000-04

    THE PHYSIOLOGICAL SOCIETY OF JAPAN

References:  38

Cited by:  1

Codes

  • NII Article ID (NAID)
    10008291123
  • NII NACSIS-CAT ID (NCID)
    AA00691224
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    0021521X
  • NDL Article ID
    5413543
  • 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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