A simple approach to evaluate the kinetic rate constant for ATP synthesis in resting human skeletal muscle at 7 T

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6 Scopus citations

Abstract

Inversion transfer (IT) is a well-established technique with multiple attractive features for analysis of kinetics. However, its application in measurement of ATP synthesis rate in vivo has lagged behind the more common saturation transfer (ST) techniques. One well-recognized issue with IT is the complexity of data analysis in comparison with much simpler analysis by ST. This complexity arises, in part, because the γ-ATP spin is involved in multiple chemical reactions and magnetization exchanges, whereas Pi is involved in a single reaction, Pi → γ-ATP. By considering the reactions involving γ-ATP only as a lumped constant, the rate constant for the reaction of physiological interest, kPi→γATP, can be determined. Here, we present a new IT data analysis method to evaluate kPi→γATP using data collected from resting human skeletal muscle at 7 T. The method is based on the basic Bloch–McConnell equation, which relates kPi→γATP to (Formula presented.), the rate of Pi magnetization change. The kPi→γATP value is accessed from (Formula presented.) data by more familiar linear correlation approaches. For a group of human subjects (n = 15), the kPi→γATP value derived for resting calf muscle was 0.066 ± 0.017 s−1, in agreement with literature-reported values. In this study we also explored possible time-saving strategies to speed up data acquisition for kPi→γATP evaluation using simulations. The analysis indicates that it is feasible to carry out a 31P IT experiment in about 10 min or less at 7 T with reasonable outcome in kPi→γATP variance for measurement of ATP synthesis in resting human skeletal muscle. We believe that this new IT data analysis approach will facilitate the wide acceptance of IT to evaluate ATP synthesis rate in vivo.

Original languageEnglish (US)
Pages (from-to)1240-1248
Number of pages9
JournalNMR in biomedicine
Volume29
Issue number9
DOIs
StatePublished - Sep 1 2016

Keywords

  • 7 T
  • ATP
  • T relaxation time
  • chemical exchange
  • energy metabolism
  • inversion transfer
  • magnetization transfer
  • skeletal muscle

ASJC Scopus subject areas

  • Molecular Medicine
  • Radiology Nuclear Medicine and imaging
  • Spectroscopy

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