It has been suggested that the severity of an attack of acute pancreatitis is related to the presence of intraglandular trypsinogen activation and that disease severity is also reflected by the degree of the acute-phase protein response. In this study we examine the relationships among amylase release, the degree of trypsinogen and prophospholipase A2 activation [as measured by urinary trypsinogen activation peptide (TAP) and prophospholipase A2 activation peptide (PLAP) concentrations], and the serum concentrations of the acute phase-protein C-reactive protein (CRP) and the principal mediator of the acute-phase protein response, interleukin-6 (IL-6). Twenty-four patients (14 mild and 10 severe attacks) were studied. Peak serum amylase concentrations were seen within 12 h and peak urinary TAP/creatinine (Cr) and PLAP/Cr ratios between 12 and 24 h after the onset of symptoms, preceding those of IL-6 and CRP. The integrated TAP/Cr and PLAP/Cr responses were significantly greater in those with severe disease [95% confidence internal (CI) = 106-259.6 pmol/mmol/h, p < 0.0008; and 95.1% CI = 462.2-3887 pmol/mmol/h, p < 0.003, respectively]. The integrated amylase response was not significantly greater in those with severe disease (95.6% CI = -415 to 832 IU/L/h, p < 0.14). There was a strong correlation among the integrated IL-6, TAP/Cr (r = 0.63, p < 0.01), and PLAP/Cr (r = 0.64, p < 0.01) responses but a poor correlation with the integrated amylase response (r = 0.19, NS).(ABSTRACT TRUNCATED AT 250 WORDS)