INVESTIGATION OF A PRIMARY REQUIREMENT OF ORGAN PRESERVATION SOLUTIONS - SUPPLEMENTAL BUFFERING AGENTS IMPROVE HEPATIC ENERGY-PRODUCTION DURING COLD-STORAGE

Background. This study was designed to investigate the effects of a mo dified University of Wisconsin (UW) solution supplemented with one of four buffering agents (histidine, bicine [N,N-bis(2-hydroxyethyl)glyci ne], tricine [N-tris(hydroxymethyl)methylglycine], and Tris) on liver metabolism during cold ischemic storage. Methods. Rat livers were flus hed and stored for a maximum period of 24 hr at 4 degrees C, and tissu e energetics, substrate, and anaerobic end-products were assessed; the group exhibiting the best results during storage was recovered in a 6 0-min period of warm reperfusion. Relative buffering capacities of the experimental solutions (measured over physiological pH range, in mM H +/L) were: UW, 4.1; histidine+UW, 9.8; Tris+UW, 19.0; bicine+UW, 22.5; tricine+UW, 26.8. Results. In the UW group, ATP levels dropped rapidl y over the first 4 hr; 1.0 mu mol/g (40% of initial) remained after 4 hr of storage, By 2 hr, ATP levels in bicine- and tricine-treated grou ps were 0.5 and 1.1 mu mol/g greater than in the UW-stored livers and by 10 hr, ATP in bicine-treated livers was twofold that of the control (UW) group, Total adenylate levels also reflected a superior elevatio n of cellular energetics; even after 24 hr, quantities were 1.4 and 2. 0 mu mol/g higher than the UW group in bicine- and histidine-supplemen ted organs, The increase in energetics occurred as a result of increas ed flux through the major anaerobic energy-producing pathway, glycolys is, The glycolytic rate was significantly greater at storage times > 1 0 hr with solutions supplemented with bicine, histidine, and tricine. Final values for net lactate accumulation over the entire 24-hr storag e period were: UW, 10.1 mu mol/g; histidine, 14.3 mu mol/g; bicine, 15 .2 mu mol/g; tricine, 13.8 mu mol/g. Activities of glycogen phosphoryl ase revealed that the activity of this enzyme dropped by 50% within 2 hr of storage in UW, However, histidine and bicine supplementation res ulted in a substantial elevation of phosphorylase ''a'' over 4 hr and 10 hr, respectively, The best buffer of the four examined in this stud y was bicine; energetics, glycolytic flux, and patterns of adenylate r egeneration upon reperfusion were markedly superior to modified UW sol ution. Conclusion. The results of this study suggest that supplementin g the ''gold standard'' UW solution with an additional buffering agent (in order of efficacy: bicine>tricine>histidine) may improve the meta bolic status of livers during clinical organ retrieval/storage.