The formation of free radicals after orthotopic liver transplantation in the rat correlates with graft failure. Fatty livers from alcoholics transplant poorly, so these studies were designed to examine the effect of alcohol on free radical formation in a rearterialized rat liver transplantation model. Treatment of rats for 3-5 weeks with either a high-fat or an ethanol-containing liquid diet caused characteristic pericentral lipid accumulation. After storage in University of Wisconsin cold storage solution (UW) and transplantation, a reperfusion injury characterized by increased postoperative AST levels (greater than 1500 U/l in about 3 hours) was observed in rats fed high-fat or alcohol-containing diets, whereas parenchymal cell injury was seen much less in low-fat controls. Survival was around 63% in the low-fat group but decreased to 12 and 18% in the high-fat and alcohol groups, respectively. Furthermore, intracellular lipid content correlated inversely with survival. In untransplanted livers, the spin trap alpha-phenyl N-tert-butylnitrone (PBN) was infused, and blood samples were collected and extracted with chloroform:methanol. Signals indicative of carbon-centered PBN radical adducts were barely detectable in all untransplanted groups studied by electron paramagnetic resonance. In contrast, a robust 6-line complex spectrum was obtained from all groups studied immediately after 48 hours of cold storage in UW solution and transplantation. A mixture of 3 radical species was identified. Two had coupling constants similar to lipid-derived free radicals, whereas the third is a new species with unique coupling constants and is most likely oxygen derived. In low-fat controls, the signal was reduced significantly by superoxide dismutase (SOD)/catalase; however, SOD/catalase had no effect on free radicals in lipid-loaded livers. Thus, both dietary high fat and alcohol exposure produce a unique SOD/catalase-insensitive free radical species that may be involved in the mechanism of failure of fatty livers after orthotopic liver transplantation.