To investigate the protection and mechanism of lactulose preconditioning on liver ischemia-reperfusion injury (IRI) in rats.

Forty-five Sprague-Dawley rats were randomly divided into three groups by random number table: sham-operation (SO) group, IRI group, lactulose preconditioning (lactulose) group with 15 rats in each group. Lactulose (0.1 g/ml) was administered daily via gavage in lactulose group 7 d before operation, while equal volume of normal saline was administered via gavage in IRI and SO group. In IRI and lactulose group, the portal vein and corresponding hepatic artery branches of middle and left hepatic lobes were clamped with bulldogs clamps during the operation to make 70% of the liver in ischemia, and blood supply recovered after 60 min′s blocking, and reperfusion was performed for 6 h to establish IRI model. In SO group, the rats only underwent open surgery and hepatic ligaments were exposed and separated. After operation, the levels of serum interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α were detected by enzyme linked immunosorbent assay. The morphological change of liver tissue was observed under light microscope. Hepatocyte apoptosis was observed under fluorescence microscope. The expression of activated caspase-3 was detected by Western blot. The detecting data of cytokines in rats among 3 groups were compared by one-way analysis of variance and LSD-t test.

The level of IL-1β in SO, IRI and lactulose group was (75±22), (365±30), (139±16)ng/L respectively, and the level of IL-6 was (48±16), (190±22), (92±10)ng/L respectively, and the level of TNF-α was (11.3±5.1), (40.2±2.7), (19.5±3.9)ng/L respectively. The levels of IL-1β, IL-6, TNF-α in IRI group were significantly higher than those of SO group (LSD-t=30.6, 20.6,19.4; P<0.05), while were significantly lower than those of lactulose group (LSD-t=-26.2, -16.1, -16.9; P<0.05). Normal morphology of liver tissue was observed in SO group. Large area of focal or patchy necrosis of hepatocytes was observed in IRI group. Hydropic degeneration and spotty necrosis were observed in lactulose group, and its tissue structure damage was milder than that of IRI group. No obvious apoptosis was observed in SO group. The number of apoptosis obviously increased in lactulose and IRI group, while the number of apoptosis in lactulose group was less than that of IRI group. Compared with the SO group, the expression of activated caspase-3 in lactulose group was up-regulated, but more down-regulated than the IRI group.

Lactulose preconditioning can alleviate liver IRI in rats, which may be related with the inhibition of inflammatory cytokine release and the inhibition of apoptosis.