TRYPSINOGEN ACTIVATION IN RAT PANCREATIC ACINAR-CELLS HYPERSTIMULATEDBY CERULEIN

Inappropriate trypsinogen activation is discussed as an early intracel lular event in the secretagogue-induced model of acute pancreatitis. H owever, the mechanisms by which trypsinogen is activated are not well characterized. In the present work, trypsinogen activation was studied in intact acinar cells using bis-(CBZ-arginyl)-Rhodamine 110 [(CBZ-Ar g)(2)-Rho 110] as a cell-permeant substrate for trypsin and also indep endently via the formation of trypsinogen activation peptide (TAP). Pr eincubation with 10nM caerulein increased the Rho 110-substrate cleava ge more than threefold. This proteolytic activity was fully sensitive to a benzamidine (BA)-type serine protease inhibitor. The appearance o f enzymatic activity was paralleled by the formation of TAP. The lack of effect of the high-molecular soybean trypsin inhibitor indicates an intracellular substrate cleavage. The cathepsin B inhibitor CA-074 pr evented neither the caerulein-induced formation of TAP nor the (CBZ-Ar g)(2) Rho 110-cleaving activity. BA inhibited the Rho 110-substrate cl eavage and significantly reduced the TAP formation. These results show that trypsinogen activation in caerulein-hyperstimulated acinar cells may occur independently of the activity of cathepsin B. On the contra ry, the effect of BA suggests the role of a serine protease in trypsin ogen activation. (C) 1997 Elsevier Science B.V.