BACKGROUND:?Although the use of non-heart beating donors (NHBDs) could bridge the widening gap between organ demand and supply, its application to liver transplantation is limited due to the high incidence of primary graft loss. Prevention of liver injury in NHBDs will beneift the results of transplantation. This study was conducted to evaluate the protective effects of L-arginine on liver grafts from NHBDs. METHODS:?One hundred and four Wistar rats were randomly divided into 7 groups: normal control (n=8), controls 1, 2 and 3 (C1, C2, C3, n=16), and experimental 1, 2 and 3 (E1, E2, E3, n=16). For groups C1 and E1, C2 and E2, and C3 and E3, the warm ischemia time was 0, 30, and 45 minutes, respectively. Liver grafts were lfushed with and preserved in 4 ℃ Euro-collins solution containing 1 mmol/L L-arginine for 1 hour in each experimental group. Recipients of each experimental group were injected with L-arginine (10 mg/kg body weight) by tail vein 10 minutes before portal vein reperfusion. Donors and recipients of each experimental control group were treated with normal saline. Then transplantation was performed. At 1, 3, and 24 hours after portal vein reperfusion, blood samples were obtained to determine the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), nitric oxide (NO) and plasma endothelin (ET). At 3 hours after portal vein reperfusion, grafts samples were ifxed in 2.5%glutaraldehyde for electron microscopic observation. RESULTS:?At 1 hour after portal vein reperfusion, the levels of NO in groups E1, E2, E3 and C1, C2, C3 were lower, while the levels of plasma ET, serum ALT and AST were higher than those in the normal control group (P