Ischemic injury of the small intestine studied by 31P-MRS

In order to examine the efficacy of phosphorus-31 nuclear magnetic resonance spectroscopy (31P-MRS) of the small intestine during superior mesenteric artery occlusion (SMAO) and reperfusion, we compared the beta-ATP level measured by in vivo 31P-MRS and the ATP level measured by high performance liquid chromatography (HPLC) in a rat model. The rat small intestines were subjected to 30 or 90 min of SMAO followed by reperfusion. 31P-nuclear magnetic resonance spectra were taken every 10 min during SMAO and subsequent reperfusion. Specimens for HPLC were taken every 30 min. Metabolite levels measured by 31P-MRS and HPLC demonstrated a linear correlation. This result shows that 31P-MRS can determine the ATP content of the small intestine as well as HPLC. Additionally, the changes of beta-ATP, inorganic phosphate (Pi) and tissue pH in the small intestine during SMAO and reperfusion were examined by 31P-MRS in detail. beta-ATP decreased with longer SMAO times, and the recovery rate of beta-ATP after reperfusion also decreased with longer SMAO times. Therefore, the ATP level measured by 31P-MRS may provide a clinical parameter of tissue damage and organ viability. The levels of Pi and tissue pH changed greatly, but reached a plateau in the early phase of SMAO. Their levels after reperfusion reflected the time of SMAO, and therefore may also provide a clinical parameter of organ viability.