Synthesis of extracellular matrix components is enhanced in the rat pancreas during regeneration from caerulein-induced pancreatitis. To study the involvement of transforming growth factor beta 1 (TGF beta 1), one of the most potent modulators of the extracellular matrix, in the process of pancreatic regeneration we examined the expression of this gene on the transcript and protein level. Pancreatic RNA was extracted from rats killed 0 h, 12 h, 24 h, 2, 3 and 7 days after induction of caerulein pancreatitis. Transcript levels for TGF beta 1 were measured by slot-blot analysis and mRNA in situ hybridization. Total amount of TGF beta 1-protein was measured using a radioligand binding assay. TGF beta 1 protein was increased twofold after 24 h and 48 h and returned to control values 7 days after induction of pancreatitis, TGF beta 1-mRNA reached maximal values (3-fold over controls) after 2 days. The largest amount of TGF beta 1-mRNA was found in pancreatic acinar cells and in stromal cells. In summary, expression of TGF beta 1 in acinar and stromal cells of the rat pancreas is enhanced during regeneration from caerulein-induced pancreatitis, which may indicate an involvement of TGF beta 1 in the regulation of extracellular matrix regeneration in the rat pancreas after caerulein-induced pancreatitis.