Measurement of spin-lattice relaxation times and kinetic rate constants in rat muscle using progressive partial saturation and steady-state saturation transfer

Alena Horská, Richard G.S. Spencer

Research output: Contribution to journalArticlepeer-review

Abstract

31P spin-lattice relaxation times (T1) of metabolites in rat calf muscle at 1.9 Tesla and the forward rate through the creatine kinase (CK) reaction have been measured using a new method based on modeling progressive saturation explicitly incorporating the effect of chemical exchange. In a separate series of experiments, we compared our method with inversion recovery both in vitro and in vivo, finding agreement between the techniques. We found that the T1 values of phosphocreatine (PCr) (6.6 ± 0.3 s), γ-ATP (2.6 ± 0.6 s), α-ATP (2.4 ± 0.4 s) and β-ATP (2.2 ± 0.2 s) are unchanged by stimulation of sufficient intensity to induce a 32% drop in PCr level. The errors in T1 values which arise when chemical exchange is neglected are calculated. These are found to be on the order of 20% for PCr and 30-50% for γ-ATP under typical conditions. Use of longer repetition times results in larger errors in measured values of T1. This source of error can be effectively eliminated by use of sufficiently short repetition times. We found that the rate constant of the forward CK reaction was increased 60% by stimulation, from 0.20 ± 0.03 s-1 to 0.32 ± 0.05 s- 1, but that the phosphorus flux did not change.

Original languageEnglish (US)
Pages (from-to)232-240
Number of pages9
JournalMagnetic resonance in medicine
Volume36
Issue number2
DOIs
StatePublished - Aug 1996

Keywords

  • NMR
  • creatine kinase
  • muscle
  • spin-lattice relaxation time

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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