This study compares the effects of machine perfusion (MP) at different temperatures with simple cold storage. In addition, the role of Ca2+ levels in the MP medium was evaluated. For MP, rat livers were perfused for 6 hours with Krebs-Henseleit (KH) solution (with 1.25 or 2.5 mM CaCl2) at 4°C, 10°C, 20°C, 25°C, 30°C, or 37°C. For cold storage, livers were perfused in situ and preserved with Celsior solution at 4°C for 6 hours. The reperfusion period (2 hours at 37°C) was performed under the same conditions used for MP-preserved and cold storage-preserved livers. Hepatic enzyme release, bile production, adenosine triphosphate (ATP) levels, and morphology were evaluated during MP and reperfusion. MP at 37°C caused marked enzyme release; the same findings were obtained during reperfusion. By contrast, MP temperature lowering induced a significant decrease in liver damage. High levels of biliary gamma-glutamyltransferase and lactate dehydrogenase were found with MP at 4°C and 10°C but not with MP at 20°C. When a KH-1.25 mM CaCl2 solution was used during MP at 20°C, very low enzyme release was observed and significantly lower hepatic damage was present at the end of the reperfusion period in comparison with cold storage. The same results were obtained when ruthenium red, a calcium uniporter blocker, was added to KH-2.5 mM CaCl2 ATP levels were higher and morphology was better in liver preserved with KH-1.25 mM CaCl2 MP at 20°C with KH-1.25 mM CaCl2 resulted in better quality liver preservation, improving hepatocyte and endothelial biliary cell survival, in comparison with cold storage. This raises the need to reconsider the temperature and calcium levels to be used during liver MP.
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