Comparison of in vivo and ex vivo porcine liver function using the same liver

In vivo and ex vivo liver function was compared using the same livers to exclude interanimal variation in hepatic function. Six male pigs were anesthetized, and catheters and perivascular flow probes placed for transhepatic sampling and hepatic arterial and portal venous flow measurement. After a 2-h in vivo study period, the livers were resected and studied immediately afterwards for a further 2 h ex vivo as an isolated perfused preparation (Experiment A). Hepatic function in a further 6 pig livers (Experiment B) was studied ex vivo only for comparison with the ex vivo livers from Expt. A to determine whether the prior in vivo study had affected hepatic function. Despite using the same livers with similar total hepatic blood flows, (0.91 ± 0.16 ml·g^-1 ·min^-1) in vivo and (0.84 ± 0.03 ml·g^-1·min^-1) ex vivo, hepatic oxygen consumption (6.5 ± 0.9 vs 2.6 ± 0.2 ml O₂·100 g^-1), adenosine-5-triphosphate content (5.22 ± 0.62 vs 4.14 ± 0.71 μM·g liver^-1) and bile flow (15.1 ± 1.2 vs 6.0 ± 1.0 ml·h^-1) were initially less ex vivo and remained so throughout the study, while perfusate potassium (initially) (3.7 ± 0.1 vs 6.4 ± 0.3 meq·1^-1), and aspartate aminotransferase (50 ± 9 vs 76 ± 5UL^-1) was consistently higher than in vivo values. Initial hepatic energy charge (0.620 ± 0.034 vs 0.552 ± 0.061) and total adenine nucleotides (12.49 ± 0.60 vs 11.66 ± 0.62 μM·g liver^-1) were not different and remained so subsequently. There was a significantly lower potassium perfusate concentration (initially, 5.1 ± 0.4 vs 6.4 ± 0.3 meq·1^-1), and higher hepatic ATP content (5.65 ± 0.29 vs 4.27 ± 0.71 μM·g liver^-1) and energy charge (0.755 ± 0.016 vs 0.574 ± 0.031) ex vivo in the group of livers not previously studied in vivo (Expt. B) when compared with the ex vivo livers from Expt. A, whilst adenosine-5-diphosphate (2.55 ± 0.17 vs 4.77 ± 0.34 μM·g liver^-1) and adenosine-5-monophosphate (0.98 ± 0.10 vs 2.49 ± 0.38 μM·g liver^-1) and TAN (9.20 ± 0.35 vs 11.56 ± 0.52 μM·g liver^-1) was significantly lower despite similar values for hepatic oxygen consumption, bile flow and AST perfusate concentration. This suggests that the prior in vivo study has important effects on the energy state of livers perfused immediately afterwards which may be detrimental to hepatic function and would mitigate against using this methodology for the comparison of in vivo and ex vivo hepatic function.