We studied the effect of total body X-irradiation and partial hepatectomy on the acute phase protein gene expression in rat liver. Male rats of AO strain were irradiated with high X-ray doses, without any visible tissue damage. In contrast, partial hepatectomy consisted of surgical removal of 40% liver tissue. The changes in liver mRNA concentrations for positive acute-phase reactants including cysteine protease inhibitor, alpha(1)-acid glycoprotein, fibrinogen and haptoglobin, and albumin as a negative reactant were monitored by Northern blot and slot-blot hybridizations using corresponding [32P]dCTP labeled cDNA probes. While in the first 24 h after the partial hepatectomy, liver mRNA levels for the positive acute-phase reactants increased, briefly followed by an immediate decrease, the duration and timing of the acute-phase responses to the whole body X-irradiation were slightly different and lasted for as long as 72 h. Although both treatments induced the mRNA expression of acute-phase reactants in rat liver, the observed variations in the duration and intensity of the changes in mRNA levels for the acute-phase proteins in these two types of tissue damage suggest the involvement of specific mechanisms in a fine tuning of the non-specific acute-phase responses to meet the unique requirements of the particular injury.