Non‐Invasive in Vivo Determination of the Absolute ATP Concentration in the Rat Liver by 31P NMR Spectroscopy

The concentration of ATP in the rat liver was determined in vivo by means of surface coil 31P NMR spectroscopy. The double standard method was used in order to achieve absolute quantification of ATP through its 31P β-resonance. Contamination of the 31P NMR liver spectra by contributions from abdominal muscle tissue was minimized by applying the FROGS presaturation sequence. Difficulties inherent to the B1 inhomogeneity of surface coils were overcome by the use of adiabatic half passage sech/tanh RF pulses. While in the normal rat liver the mean ATP concentration was 3.39 ± 0.31 mM, fibrotic rat livers exhibited a significantly lower average ATP concentration of 2.29 ± 0.31 mM.