This study assessed the hepatic acute phase response and cellular Ca2regulation in septic animals and in hepatoma cell linesin vitro. Sepsis was induced in male Sprague-Dawley rats by implanting in their abdominal cavities fecal pellets impregnated with liveEscherichia coliandBacteroides fragilis. 8 h after implantations, rats were treated with diltiazem (1.2 mg/kg) or superoxide dismutase (SOD) (5 x 103units/kg). After 24 h, plasma acute phase proteins (APP) were determined by immunoelectrophoresis, and hepatic APP-mRNAs by Northern blot hybridization. Effects of diltiazem, verapamil, or SOD on hepatic cells were determined in rat Reuber H-35 and human HepG2 hepatoma cells. Sepsis induced a significant increase in plasma APP and their hepatic mRNAs. Diltiazem and SOD reduced the sepsis-induced elevations in plasma lactate, the febrile response and mortality. APP expression in H-35 and HepG2 cells, stimulated by interleukin 1 (IL-1), IL-6, and dexamethasone, was inhibited by diltiazem or verapamil but not SOD. The results suggest that a heightened hepatic APP response in septic animals accompanies systemic/metabolic derangements and a significant animal mortality. Because diltiazem was previously shown to prevent sepsis-related disturbances in hepatic cellular Ca2regulation, its mediation of decrease in APP, systemic/metabolic response and mortality may be effected through modifications in cellular Ca2regulation. The data from hepatoma cells show an attenuation of the AAP can result from direct effects of a calcium blocker. However, whether the blocker primarily modifies cellular Ca2regulation and secondarily effects APP gene expression, or directly effects gene expression remains unknown.