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A simple approach to evaluate the kinetic rate constant for ATP synthesis in resting human skeletal muscle at 7 T
Author(s) -
Ren Jimin,
Sherry A. Dean,
Malloy Craig R.
Publication year - 2016
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3310
Subject(s) - magnetization transfer , pi , reaction rate constant , magnetization , chemistry , constant (computer programming) , thermodynamics , mathematics , biophysics , biological system , kinetics , computer science , physics , biochemistry , biology , medicine , quantum mechanics , magnetic field , magnetic resonance imaging , radiology , programming language
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 P i is involved in a single reaction, P i → γ‐ATP. By considering the reactions involving γ‐ATP only as a lumped constant, the rate constant for the reaction of physiological interest, k Pi→γATP , can be determined. Here, we present a new IT data analysis method to evaluate k Pi→γATP using data collected from resting human skeletal muscle at 7 T. The method is based on the basic Bloch–McConnell equation, which relates k Pi→γATP tom ˙ Pi , the rate of P i magnetization change. The k Pi→γATP value is accessed fromm ˙ Pi data by more familiar linear correlation approaches. For a group of human subjects ( n = 15), the k Pi→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 k Pi→γATP evaluation using simulations. The analysis indicates that it is feasible to carry out a 31 P IT experiment in about 10 min or less at 7 T with reasonable outcome in k Pi→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 . Copyright © 2015 John Wiley & Sons, Ltd.