Hepatocyte transplantation (HcTX) has been investigated for many years as an alternative therapy to orthotopic liver transplantation to treat hepatic congenital enzymatic deficiency disease. The animal model most used is the Gunn rat, which presents a hyperbilirubinemia caused by the lack of uridine-diphosphate-glucuronyl-transferase. Some investigators have clearly described a hepatotrophic effect mediated by islets of Langerhans (IL) when transplanted with hepatocytes (Hc). In this study, the functional effect of cotransplanted IL on hepatocytes (co-HcTX) in Gunn rats in an isograft model is assessed.