The aim of this study was to assess the effects of parenteral alanyl-glutamine dipeptide (Ala-Gln) on TPN-associated liver injury. Forty-three New Zealand rabbits (6-8 days old) were divided into three groups: 12 in the control group (maternal fed); 18 in the TPN group (TPN for 10 days); 13 in the Gln-PN group (TPN+Ala-Gln 400 mg kg(-1) day(-1) for 10 days). At the end of the experiment, liver function and histology were evaluated; MDA content of liver tissues and hepatocyte apoptosis by TUNEL assay were also determined. The serum concentration of direct bilirubin and bile acid in the Gln-PN group was significantly lower than TPN group (P < 0.05), but showed no difference compared with the control group. AST level of the Gln-PN group was lower than the other two groups. The light microscopy (LM) features in the TPN group included cholestasis or diffuse steatosis, while in the Gln-PN group, inflammatory infiltration and mild hydropic degenerative changes were mainly found without obvious cholestasis or proliferation of bile ducts. The electron microscopy appearances corresponded with LM findings. The liver MDA content in the Gln-PN group was clearly lower than the TPN group (P < 0.05), and was lower without statistical significance compared with control group. TUNEL assays showed the ratio of apoptotic hepatocytes in the TPN group was the highest among all the groups (44.59 +/- 6.68 vs. 0.92 +/- 0.85 in the control group, P < 0.01; 44.59 +/- 6.68 vs. 4.14 +/- 2.76 in the Gln-PN group, P < 0.01). There were significantly fewer apoptotic hepatocytes in the Gln-PN group. From this study, we found that glutamine dipeptide supplementation could attenuate TPN-associated liver injury in infant rabbits, and could also decrease liver MDA production and hepatocyte apoptosis during total parenteral nutrition.