Trypsin(ogen) content of pancreatic calculi in chronic calcified pancreatitis in man.

Protein analysis of intraductal precipitates and calculi is important to elucidate the mechanism of stone formation in chronic pancreatitis. We revealed human cationic trypsin immunoreactivity in protein extracts of pancreatic stones from 11 of 13 patients with chronic calcified pancreatitis, ranging from 0 to 42.3 ng/micrograms protein. On gel filtration the immunoreactivity eluted as one peak, which is identical to that of human cationic trypsinogen. On immunostaining of pancreatic stone, using an immunogold technic and scanning electron microscopy, the immunoreactivity was observed more densely in the amorphous portion of the center of the stones than in the concentric laminar layer of the periphery. Only negligible activity was detected for elastase 1 or amylase in the stone extracts. These results suggest that the presence of trypsinogen in pancreatic stone is not due to coprecipitation or adsorption of pancreatic enzymes but that trypsinogen is more likely involved in an initial step of intraductal precipitate formation than in a subsequent step of stone formation. However, the absence of trypsinogen in the stones from two of the 13 patients also suggests that trypsinogen is not the sole protein initiating precipitate formation.