BENEFICIAL EFFECT OF ALANINE ON METABOLIC RECOVERY OF FASTED LIVERS SUBMITTED TO COLD ISCHEMIA

The aim of this study was to investigate the possible beneficial effec t on perfused mouse liver of alanine as an exogenous substrate for glu coneogenesis. Livers from fed and fasted animals were perfused with ox ygenated Krebs' Henseleit buffer for 30 min, then stored at 4 degrees C in University of Wisconsin solution for 48 h. Then reperfusion at 37 degrees C was performed according to two protocols. In the first one, reperfusion with alanine-free Krebs' Henseleit buffer was used for 1 h, 8 mM (3-C-13) alanine was then added and perfusion was prolonged fo r a second hour. In the second one, the first hour of perfusion was om itted and the organs were reperfused directly for an hour in the prese nce of 8 mM (3-C-13)alanine, P-31 NMR was used to measure the NTP reco very of the livers. At the end of the reperfusions, C-13 and H-1 NMR s pectra of perfusates and of glutamine extracted from these perfusates by HPLC were recorded. These data were analysed according to a model o f liver metabolism assuming that the only substrate of the liver was ( 3-C-13)alanine and endogenous substrates were metabolizable only throu gh pyruvate. It was found that in the absence of initial alanine at re perfusion, livers from fasted mice recovered less NTP than those of fe d ones (40 +/- 4% vs 60 +/- 5%, p < 0.01), but not if this substrate i s present at the beginning of reperfusion (61 +/- 5% vs 60 +/- 5%). Th is was confirmed by the amount of labelled metabolites produced. Howev er, the dilution of C-13 labelled metabolites by unlabelled ones did n ot indicate a larger concentration of endogenous substrates in livers from fed mice. The conclusion reached was that the lower pyruvate dehy drogenase activity of livers from fasted mice relatively to that from fed mice could be compensated for by the greater pyruvate concentratio n provided by alanine for the initial production of NTP after cold isc hemia and warm reperfusion.