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

Academic Article

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 mumol/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 (approximately 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.(ABSTRACT TRUNCATED AT 250 WORDS)

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    Keywords

  • Adenosine Triphosphate, Analysis of Variance, Animals, Cardiomegaly, Energy Metabolism, In Vitro Techniques, Lactates, Magnetic Resonance Spectroscopy, Male, Myocardial Ischemia, Perfusion, Phosphocreatine, Phosphorus Isotopes, Rats, Rats, Sprague-Dawley, Sodium, Sodium Isotopes, Time Factors, Ventricular Fibrillation

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    Author List

  • Pike MM; Luo CS; Yanagida S; Hageman GR; Anderson PG

    • Start Page

  • 394

    • End Page

  • 406

    • Volume

  • 77

    • Issue

  • 2