HYPOTHERMIC PERFUSION PRESERVATION OF LIVER - THE ROLE OF PHOSPHATE IN STIMULATING ATP SYNTHESIS STUDIED BY P-31 NMR

Hypothermic perfusion of rat livers was investigated by (31)phosphorus nuclear magnetic resonance (P-31 NMR) spectroscopy using a temperatur e-controlled module that allowed data acquisition at various time poin ts during a 48-h period. The livers were perfused with an oxygenated l actobionate/raffinose-based solution containing adenosine and inorgani c phosphate, and changes in tissue oedema were monitored by direct on- line measurements of liver weight changes. Liver tissue ATP concentrat ions, determined by fluorimetric assay, were low immediately after org an removal, probably reflecting metabolic stress during the removal pe riod, and these increased slightly during the next 3 h. This was refle cted by changes in the P-31 NMR spectra. However, by 24 h ATP levels h ad increased significantly, and these were maintained for up to 48 h, suggesting a shift in the balance between energy production and consum ption. When inorganic phosphate was replaced by another anion (citrate ), ATP was maintained at a constant lower level during perfusion for 4 8 h. Tissue weight changes were similar in both groups, suggesting tha t volume control was not affected by the different ATP contents of the livers. By combining the temperature-controlled module with a separat e perfusion circuit, NMR spectroscopy can provide a sensitive method f or following energy metabolism in the same organ over long periods dur ing hypothermic perfusion.