Assessment of human liver metabolism by phosphorus-31 magnetic resonance spectroscopy

Phosphorus 31 magnetic resonance (MR) spectroscopy was used for the study of liver metabolism in vivo in seven healthy subjects. Subjects were examined in a 1.6 T whole-body magnet using surface coils for data acquisition. The region of the liver from which MR signals were collected was selected by magnetic-field profiling. The concentration ratios of adenosine triphosphate (ATP), inorganic phosphate (Pi) and sugar phosphates contained in liver cells could be reproducibly assessed. Cytosolic pH and the free magnesium concentration were determined to be 7.18 and 300 microM, respectively. During intravenous fructose tolerance tests the hepatic concentrations of sugar phosphates, ATP and Pi altered markedly. During the first 5 min following bolus injection of 250 mg fructose/kg body weight the concentration of sugar phosphates increased sevenfold whereas Pi and ATP decreased by three- to fourfold. Metabolism of sugar phosphates was complete within 20 min and could be followed by 31P MR with a time resolution of 5 min. Thus, 31P MR spectroscopy yields insight into liver metabolism which has not been accessible so far using conventional non-invasive methods. In conjunction with intravenous fructose loading, 31P MR spectroscopy may provide a means for the functional assessment of the liver.