Objective To investigate the effects of preconditioning with ω-3 polyunsaturated fatty acid (ω-3 PUFA) on the second liverinjury in rats with traumatic brain injury and hemorrhagic shock (TBIS) and explore the underlying mechanism.Methods Total of 36 maleWistar rats were assigned randomly (random number) into 3 groups (n =12 in each)sham operation group (C),TBIS model group and PUFA pretreatment group.The arterial blood samples were taken for determination of serum levels of ALT,AST and TNF-α.The liver were removed for determination of levels of superoxide dismutase (SOD),malondialdehyde (MDA) and glutathione (GSH),and microscopic examination.Results Compared with group C,the serum levels of ALT,AST and TNF-α and the liver levels of MDA were significantly higher (P <0.01),but the liver levels of SOD and GSH in group TBIS and group PUFA were significantly lower (P <0.01).The serum levels of ALT,AST and TNF-α and the liver levels of MDA were significantly lower (P < 0.01 or P < 0.05),but the levels of SOD and GSH in livertissues were significantly higher (P < 0.01or P < 0.05) in group PUFA than those in group TBIS.Histological examination revealed the injury of liver in TBIS group,and the rats in PUFA treated group showed alleviated severity of liverinjury.Conclusions The supplementation of ω-3 PUFA can ameliorate acute liverinjury in rats with TBIS,which may contribute to inhibition of oxygenfree radicals and inflammatory cytokines expression.