Studies were carried out to investigate the effects of prostaglandin E1 (PGE1) pretreatment on normothermic liver ischemia. Mixed-breed dogs were divided into three groups: a control group, a group with induced liver ischemia, and a group pretreated with PGE1 followed by induced liver ischemia. Liver ischemia was induced by the Pringle procedure for 60 min. PGE1 was administered intravenously to some dogs at a dose of 0.5 microgram/kg/min for 30 min prior to the Pringle procedure. Sham operations were performed without induction of liver ischemia in control animals. Insulin, glucagon, and glucose metabolic clearance rates were examined before and after the Pringle procedure in the control and experimental groups. Insulin and glucose metabolic clearance rates decreased 5 min after declamping in the ischemic group, while the glucagon metabolism was not affected, and lipid peroxide production increased. In contrast, hepatic insulin metabolism improved, and lipid peroxide production normalized in the ischemic group which was pretreated with PGE1. This study suggests that PGE1 prevents hepatic metabolic disturbances due to warm ischemia and subsequent reperfusion.