23Na and 31P nuclear magnetic resonance studies of ischemia-induced ventricular fibrillation: Alterations of intracellular Na+ and cellular energy

M. M. Pike, C. S. Luo, S. Yanagida, G. R. Hageman, P. G. Andersen

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

To clarify the role of Na+i, pHi, and high-energy phosphate (HEP) levels in the initiation and maintenance of ischemia-induced ventricular fibrillation (VF), interleaved 23Na and 31P nuclear magnetic resonance spectra were collected on perfused rat hearts during low-flow ischemia (51 minutes, 1.2 mL/g wet wt). When untreated, 50% of the hearts from normal (sham) rats and 89% of the hypertrophied hearts from aorticbanded (band) rats (P<.01 versus sham) exhibited VF. Phosphocreatine content was significantly higher in sham than band hearts during control perfusion (53.3±1.6 versus 39.8±2.0 μmol/g dry wt). Before VF at 20 minutes of ischemia, Na+i accumulation was greater in hearts that eventually developed VF than in hearts that did not develop VF for both band and sham groups (144% versus 128% of control in sham; P<.005) and was the strongest metabolic predictor of VF; ATP depletion was also greater for VF hearts in the sham group. Infusion of the Na+-H+ exchange inhibitor 5-(N,N-hexamethylene)-amiloride prevented VF in sham and band hearts; reduced Na+i accumulation but similar HEP depletion were observed compared with VF hearts before the onset of VF. Rapid changes in Na+i, pHi, and HEP began with VF, resulting in intracellular Na+i overload (≈300% of control) and increased HEP depletion. A delayed postischemic functional recovery occurred in VF hearts, which correlated temporally with the recovery of Na+i. In conclusion, alterations in Na+i were associated with spontaneous VF transitions, consistent with involvement of excess Na+i accumulation in VF initiation and maintenance and with previously reported alterations in Ca2+i with VF. Hypertrophied band hearts exhibited enhanced susceptibility to ischemia-induced VF, possibly linked to a lower HEP reserve.

Original languageEnglish (US)
Pages (from-to)394-406
Number of pages13
JournalCirculation research
Volume77
Issue number2
DOIs
StatePublished - Aug 1995
Externally publishedYes

Keywords

  • Cardiac hypertrophy
  • Intracellular Na
  • Ischemia
  • Nuclear magnetic resonance
  • Ventricular fibrillation

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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