This study was performed to clarify the mechanisms underlying post-resection changes in liver cell proliferation and metabolism. To assess the role of gut-derived endotoxaemia and endogenous cytokines in these changes, the effects of peri-operative treatment with either the lipopolysaccharide-neutralizing bactericidal/permeability-increasing protein or interleukin-1 receptor antagonist were investigated at 24 h after two-thirds hepatectomy in rats. Peri-operative treatment with either agent caused enhanced expression of proliferating cell nuclear antigen (PCNA) and reduced lipid accumulation. Activity of the hexose monophosphate shunt was significantly decreased after partial hepatectomy and restored by interleukin-1 receptor antagonist only. After partial hepatectomy, bile canalicular alkaline phosphatase activity was significantly increased in pericentral zones and redistributed to both bile canalicular and sinusoidal membranes of hepatocytes. These effects were not significantly influenced by either treatment. It is concluded that endotoxin restricts liver cell proliferation and leads to lipid accumulation following partial hepatectomy, and that interleukin-1 is a principal mediator in these processes. Furthermore, interleukin-1 mediates a repression of the pentose phosphate pathway. These changes may be of significance with respect to liver function, at least in the early phase after partial hepatectomy.