Oxygen consumption is less in rat hearts arrested by low calcium than by high potassium at fixed flow

D. Burkhoff, R. Kalil-Filho, G. Gerstenblith

Research output: Contribution to journalArticle

Abstract

The purpose of the present study was to determine whether myocardial oxygen consumption (MV̇O2) differs when the heart is arrested by hyperkalemic arresting solution (AS(K)) or by hypocalcemic arresting solution (AS(Ca)) when coronary flow is maintained constant. MV̇O2 was measured in 12 isolated, Langendorff-perfused rat hearts alternately perfused with AS(K) (20 mM K+ and 1.5 mM Ca2+) and AS(Ca) (5 mM K+ and 0.08 mM Ca2+). Six of the hearts were perfused with AS(K) for 10 min, AS(Ca) for 5 min, AS(K) for a second 5 min, and finally AS(Ca) for 5 min; AS(Ca) and AS(K) were opposite in this sequence for the other six hearts. Measurements of MV̇O2 during AS(K) and AS(Ca) arrest, taken at the end of each perfusion period, were analyzed to distinguish the independent influences of time and perfusate composition on MV̇O2 in the arrested hearts (analysis of covariance). Consistent with previous findings, MV̇O2 decreased with time after the onset of cardiac arrest with both solutions. The average per minute fall was 0.0003 ml O2·min-1·g-1 (P < 0.01). However, at any given time after arrest, MV̇O2 averaged 0.004 ml·min-1·g-1 less during AS(Ca) arrest than during AS(K) arrest (P < 0.01), which amounted to a 15% reduction in MV̇O2. To test whether the increased MV̇O2 during hyperkalemic arrest was dependent on calcium in the perfusion medium, a third series of six hearts was studied in which MV̇O2 values measured during AS(Ca) and AS(K) arrest were compared with those measured during arrest by hyperkalemic-hypocalcemic solution (AS(K,Ca): 20 mM K+, 0.08 mM Ca2+). MV̇O2 measured during AS(K,Ca) arrest was not different from that during AS(Ca) arrest (P > 0.2) and was less than MV̇O2 measured during AS(K) arrest (P < 0.05). Thus MV̇O2 of the arrested heart measured at constant coronary flow is greater during hyperkalemic arrest than during hypocalcemic arrest; furthermore, the increased MV̇O2 during hyperkalemic arrest is calcium dependent.

Original languageEnglish (US)
Pages (from-to)H1142-H1147
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume259
Issue number4 28-4
DOIs
StatePublished - 1990

Keywords

  • calcium
  • cardiac metabolism
  • cardioplegia
  • coronary resistance

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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