31P-MR spectroscopic studies of rabbit liver during ischemia

The effects of ischemia and reperfusion on hepatic energy metabolism were studied in four white rabbits (about 2.0 kg) using P-31 magnetic resonance spectroscopy (MRS). The hepatic ischemia was induced by clamping the portal vein and hepatic artery. Hepatic ischemia was continued for 19 minutes in three rabbits and 32 minutes in one. P-31 MRS was carried out using a 2.0-T whole-body MR imager and a solneoid RF coil fitted around the liver. A rapid reduction of the β-ATP peak and a rapid increase in that of inorganic phosphate (Pi) can be seen after the onset of ischemia. After 19 minutes the β-ATP peak dropped to 20 % of its original value, and the Pi peak rose to 347 %. Twenty-five minutes after reperfusion, the β-ATP peak returned to 77 % and the Pi peak dropped back to 155 %. Neither peak showed a complete recovery. The PME peak also showed a rapid increase after the onset of ischemia, reaching 224 % after 19 minutes. In contrast to the β-ATP and Pi peaks, however, it showed almost complete recovery (109 %) after 25 minutes of reperfusion. The PDE peak showed no remarkable change during ischemia and reperfusion. The rabbit subjected to 30-minutes of ischemia died during reperfusion. The β-ATP peak had dropped to 27 % when reperfusion was started, but failed to rise again. The Pi peak began to drop at the start of reperfusion, but the PEM peak continued to rise. The reduction in the ATP peak almost equaled result of biochemical assay of freeze-clamped tissue, indicating that P-13 MRS using a whole-body MR imager is useful in studying the effects of hepatic ischemia on hepatic energy metabolism. The ATP level did not recover completely even after only 19 minutes of ischemia, showing that irreversible deterioration of hepatic energy metabolism can easily be caused by even short periods of hepatic ischemia. (J.P.N.)