Method for quantifying the contribution of overlying tissue to rat liver 31P-NMR spectra using the surface-coil...

A method for quantitatively analyzing the overlying tissue contribution to the in vivo 31P-NMR spectra from rat liver observed by the surface-coil technique is presented. The peak area of beta-ATP obtained either through the abdominal wall or directly from the liver was compared before and after occlusion of the portal vein or infusion of fructose. The phosphocreatine (PCr) signal is a characteristic signature of the 31P spectrum of muscle, and did not differ before and after portal vein occlusion or fructose infusion. After 30 min of occlusion, the beta-ATP obtained through the abdominal wall decreased to 25% of its initial value and that taken directly from the liver almost disappeared. Accordingly, the overlying tissue contribution to the in vivo liver spectra could be quantitatively assessed from the post-occlusion reduction of the beta-ATP peak in the spectra. The recovery of the beta-ATP concentration 10 min after fructose infusion should also reflect the augmentation of ATP synthesis in the liver. The difference of 25% in beta-ATP concentration between the spectra obtained through the abdominal wall and those directly from the liver following fructose infusion showed the overlying tissue contribution. We demonstrated that this contribution was 25% for the liver spectra obtained through the abdominal wall and 75% of the components in the spectra originated from the rat liver in our surface-coil measurements.