BACKGROUND: Prostaglandin E-1 (PGE(1)) treatment of humans and rodents during acute hepatic failure ameliorates different parameters of hepatic dysfunction. PURPOSE: To investigate whether prevention of acute liver injury induced by D-galactosamine (D-GalN) with preadministration of PGE(1) is correlated with a change in the concentration of two proinflammatory cytokines, as tumour necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1 alpha, and/or nitrite+nitrate (NOx), as nitric oxide-related end products in serum. RESULTS: D-GalN significantly increased alanine aminotransferase (ALT) and TNF-alpha concentration in serum 5 and 10 mins, respectively, after treatment compared with the control group (P less than or equal to 0.05). D-GalN did not change the IL-1 alpha concentration at any time during the study. Preadministration of PGE(1) to D-GalN-treated rats significantly reduced the ALT content and increased significantly the TNF-alpha concentration in serum 1, 2.5, 5 and 10 mins after D-GalN treatment compared with the D-GalN group (P less than or equal to 0.05). Nitric oxide was not involved in either the toxic effect due to D-GalN or the protection observed with PGE1 against D-GalN toxicity. CONCLUSIONS: Acute liver injury induced by D-GalN is correlated with an increased TNF-alpha release. Preadministration of PGE1 to D-GalN-treated rats exerted a priming effect on inflammatory cells to release enhanced levels of TNF-alpha but not IL-1 alpha. These findings indicate that stimulation of TNF-alpha release may be involved in the acute D-GalN-induced liver injury and also in PGE(1) protection from hepatotoxicity in clinical and experimental studies.