31 P NMR assessment of orthotopic liver rejection in a rat model

31 P NMR spectroscopy was used serially to study rejecting (ACI→LEW) and nonrejecting (ACl→ACl) orthotopic liver transplants in rats. Recipients were evaluated on post‐transplant days 1,3, 5, 7, 9, and 11. The relative changes in phosphomonoester (PME), inorganic phosphate (P i ), high‐energy phosphates and pH were studied. The earliest significant difference between the rejecting and nonrejecting groups was a decrease in the α‐NTP peak area on Day 5. This was followed by significant decreases in β‐NTP and pH, and increases in PME and P i on Day 7. High‐resolution 31 P NMR spectra of perchloric acid extracts demonstrated the PME increase to be due mainly to elevated phosphoethanolamine. Using the parameter (P i + PME)/(α + β + γ‐NTP), rejecting livers were distinguished from nonrejecting livers at a moderate stage of rejection.