Absence of pH changes during altered work in the in vivo sheep heart: a 31P-NMR investigation

J Mol Cell Cardiol. 1990 May;22(5):543-53. doi: 10.1016/0022-2828(90)90956-3.

Abstract

Saturation transfer from gamma-ATP to inorganic phosphate was used to assign the intracellular inorganic phosphate resonance of the phosphorus-31 nuclear magnetic resonance spectrum of heart obtained from adult sheep under Halothane anesthesia. The 31P chemical shift of intracellular inorganic phosphate was then used as a probe of myocardial pH. Resting myocardial pH was found to be 7.03 +/- 0.02. The effects of increasing myocardial work on myocardial pH were examined using external pacing and phenylephrine infusion alone or in combination to produce steady-state increases in the rate-pressure product. No alteration in myocardial pH was observed with up to 4-fold increases in rate-pressure product. No changes in high-energy phosphates were observed except at the highest rate-pressure products obtained, where small increases in inorganic phosphate and decreases in the phosphocreatine/ATP ratio were observed. In addition, the transition to a new steady state was studied with a 20-s time resolution after initiation of pacing. Again, no changes in pH or levels of phosphates were detected during the transition to increased work.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Animals
  • Blood Pressure / drug effects
  • Blood Pressure / physiology
  • Heart / drug effects
  • Heart / physiology*
  • Heart Rate / drug effects
  • Heart Rate / physiology
  • Hydrogen-Ion Concentration
  • Infusions, Intra-Arterial
  • Magnesium / metabolism
  • Magnetic Resonance Spectroscopy
  • Myocardium / cytology
  • Myocardium / metabolism
  • Phenylephrine / administration & dosage
  • Phenylephrine / pharmacology
  • Phosphocreatine / metabolism
  • Phosphorus / metabolism

Substances

  • Phosphocreatine
  • Phenylephrine
  • Phosphorus
  • Adenosine Triphosphate
  • Magnesium