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

作者：Ren Jimin; Sherry A Dean; Malloy Craig R^*

来源：NMR in Biomedicine, 2016, 29(9): 1240-1248.

DOI：10.1002/nbm.3310

• skeletal muscle
• magnetization transfer
• ATP
• chemical exchange
• T-1 relaxation time
• 7 T
• inversion transfer
• energy metabolism

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 -ATP spin is involved in multiple chemical reactions and magnetization exchanges, whereas P-i is involved in a single reaction, P-i -ATP. By considering the reactions involving -ATP only as a lumped constant, the rate constant for the reaction of physiological interest, k(PiATP), can be determined. Here, we present a new IT data analysis method to evaluate k(PiATP) using data collected from resting human skeletal muscle at 7 T. The method is based on the basic Bloch-McConnell equation, which relates k(PiATP) to Pi, the rate of P-i magnetization change. The k(PiATP) value is accessed from Pi data by more familiar linear correlation approaches. For a group of human subjects (n = 15), the k(PiATP) 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(PiATP) evaluation using simulations. The analysis indicates that it is feasible to carry out a P-31 IT experiment in about 10 min or less at 7 T with reasonable outcome in k(PiATP) 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.

• 出版日期2016-9