The functional integrity of a normothermic perfusion system using artificial blood in pig liver

BACKGROUND: We have reported already that we succeeded in developing a normothermic liver perfusion system consisting of purely artificial products such as artificial blood. The aim of this study was to ascertain the metabolic functional integrity of the liver perfused in this system. MATERIALS AND METHODS: A liver graft from a female pig weighing 20 kg was harvested in the usual manner. The perfusion solution consisted of artificial blood, L-15 medium, distilled water, bovine serum albumin, NaHCO3, NaOH, KCl, human regular insulin, 50% glucose solution, and dexamethasone. The isolated liver was perfused with this oxygenated perfusate through the portal vein at a rate of 300 ml/min for 9 h. We analyzed the changes of amino acids, ammonia, and urea concentrations in five livers, which showed high oxygen consumption (over 8 ml-O2/min during perfusion). RESULTS: Although urea did not exist in the perfusate at first, an extremely high level of the urea concentration appeared during the perfusion. On the other hand, the ammonia concentration was only slightly elevated during the perfusion. Arginine vanished from the perfusate with increases of citrulline and ornithine. Taurine was elevated with the disappearance of methionine. Alanine, glutamine, serine, histidine, and threonine concentrations decreased with an increase of the glucose concentration. Numerous liver cells exhibited PAS-positive cytoplasmic glycogen deposits not exhibited before perfusion. The ratios of branched-chain amino acids/aromatic amino acids were elevated during the perfusion. CONCLUSION: Normothermic liver perfusion using artificial blood could sufficiently maintain the functional integrity of the liver.