PROTON NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY OF LACTATE PRODUCTION IN ISOLATED RAT-LIVER DURING COLD PRESERVATION

Lactate-edited H-1 NMR difference spectra have been acquired from inta ct rat liver tissue following flushing and preservation in ice. A peak , initially at 1.26 ppm, was seen to increase in the liver tissue with preservation time. This peak was assigned to lactate, despite the fac t that its chemical shift was initially shifted by approximately -0.1 ppm relative to an externally added standard. The assignment was based on the following: (a) the peak increased over a 24-h ischemic storage period; (b) it was coupled to a signal 2.78 +/- 0.02 ppm upheld; and (c) a parallel increase in lactate was noted in perchloric acid extrac ts of tissue from the same liver. An additional peak, assigned to alan ine, was also observed during storage and was also shifted by approxim ately -0.1 ppm. Inclusion of dimethyl sulfoxide, which readily permeat es liver tissue, demonstrated that this chemical shift alteration was a tissue-specific effect. These results demonstrate that H-1 NMR spect roscopy of intact liver tissue during hypothermic ischemia is possible , though chemical shift assignments should be made with caution. (C) 1 996 Academic Press, inc.