Pseudomonas aeruginosa exotoxin A (PEA) has been generally used to induce liver injury in mice for experimental study. No PEA-induced hepatotoxicity study has ever been conducted in rats, although rats are the most common rodents used in toxicologic bioassay and pharmacological evaluation. The present study was conducted in male Wistar rats that were injected (i.v.) with PEA at doses of 0, 10, 20, 30 or 40 microg/kg body weight and evaluated at 12, 24, 36, 48 and 60 hr post-exposure (HPE). Rats exposed to PEA at 40 microg/kg died before 36 HPE, and the mortality was dose and time dependent. Liver injury was noted as increases in serum enzymes, along with alterations of liver histology in the 40 microg/kg group at 12 HPE. TUNEL-positive staining indicative of hepatocyte apoptosis was observed in the 20 microg/kg group at 12 HPE. Significant levels of DNA fragmentation ladder were observed in the 30 microg/kg group starting at 24 HPE. Serum levels of TNF-alpha was increased in the 30 and 40 microg/kg groups at 48 and 24 HPE, respectively. Other cytokines, such as IL-2, IL-6, and IL-10 were also increased at various doses and times. Furthermore, the elevated serum hepatic index levels decreased significantly by dexamethasone pretreatment. In contrast, these markers were exacerbated by co-administration of a non-toxic dose LPS. In overall evaluation, the PEA-induced liver injury can be used as a model for study of hyperimmune-mediated hepatotoxicity.