The role of free radicals in the development of cerulein-induced pancreatitis was evaluated by measuring the activity of the endogenous scavengers, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSHpx), as indicators of the defense system, and the level of lipid peroxide (LPO) in the pancreas, as an indicator of the offense system. Acute pancreatitis was induced by 5 hourly intraperitoneal administrations of cerulein (50 micrograms/kg body weight), in 0.9% NaCl, to mice. The presence of acute pancreatitis was confirmed by changes in serum amylase levels and in typical microscopical features. Regarding the changes in the levels of endogenous scavengers, the SOD level was decreased significantly from a basal level of 52.6 +/- 3.94 to 43.1 +/- 2.79 mU/micrograms DNA at 6 h (p less than 0.01) to 38.8 +/- 5.18 mU/micrograms DNA at 9 h (p less than 0.05) and to 31.7 +/- 3.10 mU/micrograms DNA at 12 h (p less than 0.01) after the first intraperitoneal cerulein injection. The CAT level also decreased significantly from a basal level of 7.80 +/- 0.27 to 5.86 +/- 0.46 mU/micrograms DNA at 9 h (p less than 0.01) and to 4.52 +/- 0.21 mU/microgram DNA at 12 h (p less than 0.01). GSHpx increased from a basal level of 6.80 +/- 0.43 to 7.58 +/- 0.50 mU/micrograms DNA at 9 h and to 10.2 +/- 0.52 mU/micrograms DNA at 12 h after the first intraperitoneal cerulein injection.(ABSTRACT TRUNCATED AT 250 WORDS)