Metabolic shift in liver: correlation between perfusion temperature and hypoxia inducible factor-1α.

AIM: To study at what temperature the oxygen carried by the perfusate meets liver requirements in a model of organ perfusion. METHODS: In this study, we correlated hypoxia inducible factor (HIF)-1α expression to the perfusion temperature and the hepatic oxygen uptake in a model of isolated perfused rat liver. Livers from Wistar rats were perfused for 6 h with an oxygenated medium at 10, 20, 30 and 37 °C. Oxygen uptake was measured by an oxygen probe; lactate dehydrogenase activity, lactate release and glycogen were measured spectrophotometrically; bile flow was gravitationally determined; pH of the perfusate was also evaluated; HIF-1α mRNA and protein expression were analyzed by real time-polymerase chain reaction and ELISA, respectively. RESULTS: Livers perfused at 10 and 20 °C showed no difference in lactate dehydrogenase release after 6 h of perfusion (0.96±0.23 vs 0.93±0.09 mU/min per g) and had lower hepatic damage as compared to 30 and 37 °C (5.63±0.76 vs 527.69±45.27 mU/min per g, respectively, Ps<0.01). After 6 h, tissue ATP was significantly higher in livers perfused at 10 and 20 °C than in livers perfused at 30 and 37 °C (0.89±0.06 and 1.16±0.05 vs 0.57±0.09 and 0.33±0.08 nmol/mg, respectively, Ps<0.01). No sign of hypoxia was observed at 10 and 20 °C, as highlighted by low lactate release respect to livers perfused at 30 and 37 °C (121.4±12.6 and 146.3±7.3 vs 281.8±45.3 and 1094.5±71.7 nmol/mL, respectively, Ps<0.02), and low relative HIF-1α mRNA (0.40±0.08 and 0.20±0.03 vs 0.60±0.20 and 1.47±0.30, respectively, Ps<0.05) and protein (3.72±0.16 and 3.65±0.06 vs 4.43±0.41 and 6.44±0.82, respectively, Ps<0.05) expression. CONCLUSION: Livers perfused at 10 and 20 °C show no sign of liver injury or anaerobiosis, in contrast to livers perfused at 30 and 37 °C.