Protective effects of N‐acetylcysteine on hypothermic ischemia‐reperfusion injury of rat liver

We investigated whether intraportal injection of 150 mg/kg N‐acetylcysteine (NAC) into rats reduced hepatic ischemia‐reperfusion injury after 48 hours of cold storage and 2 hours of reperfusion. The organ was isolated and perfused to evaluate liver function. The control group received an intraportal injection of 5% dextrose. NAC increased L‐cysteine concentrations 15 minutes after injection (1.29 ± 0.11 μmol/g vs. 2.68 ± 0.4 μmol/g, P < .05). However, neither treatment modified glutathione liver concentrations relative to preinjection values. After 48 hours of cold storage and 2 hours of reperfusion, livers from NAC‐treated rats produced larger amounts of bile than those in the control group (5.04 ± 1.92 vs. 0.72 ± 0.37 μL/g liver; P < .05), and showed a significant reduction in liver injury, as indicated by reduced release of lactate dehydrogenase (679.4 ± 174.4 vs. 1891.3 ± 268.3 IU/L/g; P < .01), aspartate transaminase (AST) (13.94 ± 3.5 vs. 38.75 IU/L/g; P < .01), alanine transaminase (ALT) (14.92 ± 4.09 vs. 45.91 ± 10.58 IU/L/g; P < .05), and acid phosphatase, a marker of Kupffer cell injury (344.4 ± 89.6 vs. 927.3 ± 150.8 IU/L/g; P < .01) in the perfusate. Reduced glutathione concentrations in the perfusate were similar in the two groups (805 ± 69 vs. 798 ± 252 nmol/L/g), whereas oxidized glutathione (GSSG) concentrations were higher in the control group (967 ± 137 vs. 525 ± 126 nmol/L/g; P < .05). Reduced glutathione (GSH) concentrations in liver tissue collected at the end of perfusion were significantly higher in the NAC group (7.3 ± 0.9 vs. 4.1 ± 1.0 μmol/g; P < .05). The protective effect of NAC on cold ischemia‐reperfusion liver injury persisted when animals were pretreated with buthionine sulfoximine (BSO), a specific inhibitor of glutathione synthesis. Our results suggest that NAC enhances the concentrations of cysteine within hepatocytes, providing a substrate for glutathione synthesis during reperfusion. They also indicate that NAC has a direct protective effect on Kupffer cells, which are the first source of reactive oxygen intermediates during reperfusion. (HEPATOLOGY 1995; 22:539–545.)