NMR measurements of Na+ and cellular energy in ischemic rat heart: Role of Na+-H+ exchange

M. M. Pike, C. S. Luo, M. D. Clark, K. A. Kirk, M. Kitakaze, M. C. Madden, E. J. Cragoe, G. M. Pohost

Research output: Contribution to journalArticle

213 Scopus citations

Abstract

Interleaved 23Na- and 31P-nuclear magnetic resonance (NMR) spectra were continuously collected on perfused rat hearts subjected to low-flow ischemia (30 min, 10% flow) or zero-flow ischemia (21 min) followed by reperfusion. During untreated low-flow and zero-flow ischemia, intracellular Na+ (Na(i)/+) increased by 53 ± 11 (±SE) and 78 ± 8%, respectively, and remained elevated for zero-flow hearts. However, during both low- and zero- flow ischemia, Na(i)/+ did not increase in hearts treated with the Na+-H+ exchange inhibitor, 5-(N-ethyl-N-isopropyl)amiloride (EIPA). The pH decreases during ischemia were unchanged. EIPA treatment reduced ATP depletion during ischemia. During reperfusion from zero-flow ischemia, EIPA-treated hearts displayed more rapid and extensive recoveries of phosphocreatine and ATP. Recovery of left ventricular developed pressure was improved for zero-flow hearts treated with EIPA during the ischemic period exclusively (104 ± 13%) compared with untreated hearts (36 ± 21%). These data indicate that Na+- H+ exchange is an important mechanism for Na(i)/+ accumulation, but not for pH regulation, during myocardial ischemia. Additionally, Na(i)/+ homeostasis plays an important role in the postischemic recovery of cellular energy and ventricular function.

Original languageEnglish (US)
Pages (from-to)H2017-H2026
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume265
Issue number6 34-6
DOIs
StatePublished - 1993
Externally publishedYes

Keywords

  • cardiac function
  • ischemia

ASJC Scopus subject areas

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

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