PROTECTIVE PROPERTIES OF AMINO-ACIDS IN LIVER PRESERVATION - EFFECTS OF GLYCINE AND A COMBINATION OF AMINO-ACIDS ON ANAEROBIC METABOLISM AND ENERGETICS

Background/Aimes/Methods: In this study, we investigated the hepatopro tective effects of three storage solutions containing glycine (180 mM) , glycylglycine (180 mM), and a mixture of 20 amino acids (combined co ncentration of 180 mM) on energy metabolism and levels of glucose and lactate (as an index of glycolytic flux) in rat livers. All effects we re compared to those of livers flushed/stored with a modified Universi ty of Wisconsin solution. Results: Glycine-treatment showed no improve ment in liver energetics (ATP, ADP, AMP) and lactate accumulation; thi s solution had the lowest buffering capacity of the four tested (appro ximately 30% of the University of Wisconsin solution). The glycylglyci ne solution had the highest buffering capacity of the four solutions t ested (including University of Wisconsin solution). Complete titration of the glycine-, combined amino acids-, and University of Wisconsin s olutions (from 8.0 to pH=6,0) resulted in a minor decrease in glycylgl ycine buffer pH; pH dropped by 0.2 pH units. In glycylglycine-treated livers, energetics showed an improvement over the first 1 h cold stora ge; ATP and 'energy charge' values remained high and ADP levels (and c onsequently total adenylate contents) were 0.7-2.4 mu mol/g greater th an livers stored in University of Wisconsin solution. A 2-fold increas e in lactate accumulation suggested that the improvement in liver ener getics for the glycylglycine buffer was due to maintained flux through glycolysis brought about by enhanced buffering capacity. The solution containing a combination of amino acids exhibited maximum maintenance of liver energetics via increased glycolytic flux, despite its slight ly inferior buffering capacity (85% of University of Wisconsin solutio n). ATP levels were maintained over the first 2 h storage and ADP leve ls (and consequently total adenylate contents) were 1.2-2.1 mu mol/g g reater than University of Wisconsin solution-treated livers during the entire 24 h storage period. Energy charge values for livers treated w ith the combination of amino acids were also significantly higher than with glycine-. glycylglycine- and University of Wisconsin solution-tr eatment; even at 24 h, energy charge was 0.36 (comparable to only 4 h storage in University of Wisconsin solution). Conclusions: Our data su ggest that a combination of amino acids may be required for maximum pr otection of the liver, and furthermore there may be several independen t mechanisms, including buffering capacity responsible for cytoprotect ion of the liver during cold storage.